It's only when J-Lo looks me in the eye and smiles that I realise I should be doing something with my hands. And no, it's not just another night in with the Out Of Sight DVD, Jennifer Lopez is really there, three feet in front of me, in the ever-so luscious flesh. It's the Maid In Manhattan premiere and every press photographer, celebrity journo and stalker within a 50-mile radius has made their way to London's West End for a glimpse of the Latino mega-star. And I'm meant to be asking her to say cheese, to snatch a world-class digital image of a world-class star. But while I'm staring slack-jawed like an extra from Deliverance, a crowd of girls surge past me with posters, t-shirts and bare flesh to be signed, and nearby paparazzi blind me with a flurry of flashes. By the time I raise the viewfinder to my eye, realise I haven't turned my flash on, turn it on, focus and shoot, la Lopez has glided on to other hungry eyes. Although I do get a great shot of 'that' butt.

I was warned about the rabbit-in-headlights effect that famous people have on mere mortals. As a seasoned journalist I imagined myself immune to any such nonsense, especially as I effortlessly snapped top TV gardener Diarmuid Gavin on his way up the red carpet. But this is my first night as a paparazzo wannabe and I've clearly got a lot to learn. It all seemed so simple back in the office - borrow a top of the range digital camera, get familiar with its bell and whistles, then park myself outside China Whites and snap a succession of A-list slebs as they parade inside. A bit like shooting wildebeest as they stampede to a watering hole, although with fewer lions and a higher chance of getting punched. Sure, I might have to poke a telephoto lens through the odd loo window, but how hard could it be? Limping home with a handful of blurry J-Lo snaps, that Diarmuid Gavin hold-the-front-page exclusive and trainer imprints on my back from the fans, I had learned exactly how hard.

Camera Shy
One thing I did discover at the premiere is that a successful paparazzo needs more than just a quick shutter finger. By far their most important bit of kit is a mobile to tell them who's been spotted where. Most paparazzi belong to picture agencies that know exactly what's going on any night of the week, who's invited and who's not. With sources ranging from celebrity insiders to the great unwashed public, agencies can get their photographers next to almost anyone in the country in a matter of hours.

But it doesn't matter how close you get, if you're not packing heat, and a digital SLR is the hottest kit around. Canon's new 11 megapixel EOS-1Ds (£7000) is the model on everyone's lips, combining astonishing image quality with a blazing 8 frames per second and a tough, weather-resistant casing. An SLR is essential for the range of lenses it can use. Wide-angle lenses (35mm) are perfect for door-stepping houses and clubs, where you're too busy chasing cars and dodging doormen to aim or focus. If you're stuck behind a fence at premieres and photocalls, a mid-length zoom (80-200mm) lets you zoom past photographers and minders to capture just the star you're after. And of course, what better way to pay for a trip to the sun than by fitting a whacking great 600mm mirror lens and snatching a few frames of starlets frolicking in the surf?

Surprisingly enough, camera makers weren't exactly falling over themselves to lend me their top of the range SLRs for the purpose of stalking B-list celebrities, so I took the more realistic tack of lying through my teeth. Before you could say 'for review purposes only', Minolta had shipped me their flagship digicam, the semi-pro Dimage 7Hi. This has the long zoom I was after (28-200mm equivalent), a five megapixel CCD and continuous shooting modes of up to 7 frames per second. Neat features include automatic switching between the LCD screen and a colour electronic viewfinder as you put your eye to it, a Quick View mode to delete duff images on the fly, and a continuous focusing mode that keeps your main subject sharp at all times. For time-critical shoots, many paparazzi also carry laptops (titanium G4s preferred) to download images and mail them straight to the presses, but I made do with a mere 256Mb Compact Flash card.

Finding Fame
With a bag full of kit, I headed off to some of the venues that celebrities flock to like pigeons to stale Wotsits. You can usually find them suing the papers or each other at the Law Courts, but it looked like I'd chosen a quiet week for litigation. Other popular haunts are medical establishments like celebrity 'refreshment' clinic The Priory or The Portland Maternity Hospital, where the famous migrate each year to reproduce like a species of bizarre land-walking salmon. But I didn't have the time to hang around for an ex-EastEnder to OD for my convenience - I needed rock solid, 100% guaranteed superstars. And here's where I'm going to let you into a paparazzi secret, a website whose existence I'm revealing on the strict proviso that you don't pass it on to any stalker or terrorist mates. If this information got into the wrong hands, the whole cast of Emmerdale could be mobbed by literally millions of screaming fans.

Every morning, the Press Association website issues a Photo Diary that gives details of the day's premieres, awards ceremonies and photocalls, as well the movements of royalty and top politicians. And so I trotted off to Maid In Manhattan like a lamb to the slaughter. As a photo shoot it may have been a washout, but as a classroom it was drummed a few things home. I now knew to learn my C-list Hollyoaks actors beforehand, to get there early to secure a good spot, and that short, well-dressed people are generally famous (don't ask me why this one works, but it does).

Dancing Scene
I needed to test my new-found knowledge somewhere less stressful, so I blagged an invite to the launch party of dance troupe Stomp's new IMAX movie, Pulse, at Waterloo's IMAX cinema. This was more like it - no barriers, no autograph hunters, just me and two other snappers on the prowl. Here's where I learned my next lesson: accredited staff photographers working for national newspapers don't like being called paparazzi. All professions have their hierarchies, a paparazzo in photography being roughly equivalent to the bloke who wipes the arse of the guy who cleans the driver's helmet in Formula 1 racing. Instead of chatting about megapixels, I got the cold shoulder and a crappy spot behind a pillar.
Which made me feel all the better when I was first to spot Madness front man Suggs and grab him for a T3 exclusive. This being a party, I also grabbed a glass of cheeky red to celebrate, which explains the blurriness in later photos. As the evening went on, slebs and booze flowed freely, and I managed to get close-ups of comic Roland Rivron, actress Rula Lenska and lanky film critic Jonathan Ross. Despite his diminutive stature and spangly suit, I somehow failed to recognise ballet legend Wayne Sleep, although my biggest 'one that got away' was 28 Days star Naomi Harris, who has all the sex appeal of J-Lo plus the ability to fit into normal-sized knickers. But I still felt outclassed by the pros. Even my powerful Dimage couldn't keep up with the kit they used - while my flash took its precious seconds to recharge their SLRs with external battery pack zipped through a dozen frames.

For my final photo shoot, we revisited the West End for another premiere - The Life Of David Gale starring Kate Winslet and Kevin Spacey. This time everything I did everything right. We were there two hours early, staked out the best position and were packing more cameras and memory cards than your local Jessops. Only one thing was missing - the stars themselves. According to an insider at Liquid News, Kevin had 'personal problems' and Kate couldn't be arsed to show up on a rainy Sunday night. Director Alan Parker and second-billed Laura Linney (you'll remember her from Congo and The Truman Show) made the rounds, but you could tell the tourists flocking through Leicester Square were unimpressed. And so I learned my final lesson. In the end, it doesn't matter how prepared you are or how many zoom lenses or press cards you hold, if the stars aren't out, you'll go home with nothing more than a snap of the back of Bob Geldof's head.

Famous For 15 Frames
But after three nights around town, I had a half a dozen stars in the bag, from the heights of J-Lo to the depths of Roland Rivron. Everyday celebrity shots sell for thousands and global exclusives such as the first Diana/Dodi images can fetch nearer half a million, so how much were my snaps worth? Clive Dixon is in charge of buying photos for Britain's leading independent picture library, Rex Features, and supplies image to newspapers, magazines and TV stations around the world. He tried to be polite: "We rarely take celebrity shots from new photographers. The market is swamped with people who call themselves photographers - most are just opportunists with cameras. If they've got an exceptional picture or show real promise we might consider representing them but…" He didn't have to finish, I got the message. But before I hang up my paparazzi gloves, is anyone interested in the worldwide rights to my picture of top TV gardener Diarmuid Gavin? Call it a tenner and I'll throw his girlfriend in for free. Anyone?