At the Edinburgh Fringe, comedy criticsareaboutaspopularas trafficwardens.Wemaypoint peopleintherightdirection, therebyprovidingavaluable service, but we get nothing but abuse if caught with our notepads out. A symbiotic - and possibly abusive - relationship exists between comedians and critics. They view us as a necessary evil (probably more evil than necessary) while we have to endure dozens of mediocre shows in search of a handful of gems. This will be my sixth festival, and here is the most important information I've gleaned after five years on the front line.

1 Edinburgh is a goldfish bowl full of elephants during August Scotland's capital is a small city at the best of times, but during the festival the population swells so much in volume that it gets impossibly cramped. You can't escape the comedians to whom you give a bad review; it's as if with every negative word you write, your gravitational pull grows. This has been scientifically proven, as I have never met anyone I've said nice things about.

Two years ago, I reviewed a show by Richard Herring, pictured right, a regular on the BBC and a fringe veteran (this year's show Oh F****, I'm 40! - Underbelly, 8.20pm - marks his 20th year at the festival), and gave it a tepid two stars. A week later, I turned up early for the annual comedians versus critics football match, only to find Herring on the opposing team. Cue several minutes of casual chat while skilfully avoiding giving him my name. I got away with it until the kits arrived - our names were on the back. Come kick-off, Herring strode into battle screaming "Kill that f***er McCracken!" It proves, if anything, that comedians take reviewers much more seriously than we deserve.

2 Jokes about paedophilia are never funny. Ever Most comedians work at the coalface of black humour because there is a richer seam of laughter in all things negative. Take Simon Amstell's withering approach to interviewing celebrities, for example (Amstell's new show No Self is at the Pleasance Courtyard, 10.30pm). For his part, Australian shock-jock Brendon Burns purports to question what's offensive, while going all out to shock at the same time. This year, Burns is having his grubby cake and eating it with his new show So I Suppose This Is Offensive Now (Pleasance Dome, 8.30pm). But step away from the top tier of comedians and you'll find a depressingly vast legion of half-baked performers who just mention taboo subjects to get a laugh. If their poster reads "edgy", it all too often means "imagination-deficient".

3 A happy comedian is usually an unfunny comedian Like most other artforms, contentment in comedy is the greatest enemy of creativity. Which makes Josie Long one of the rarest of beasts at the Fringe - a genuinely funny comedian awash in endorphins. Long's show last year featured badge-making kits alongside five-minute monologues about why The Cure's Close To Me is quite simply the best song ever. It was an hour-long celebration, finding a sparkle of magic among mundanity where most would just complain; it made you want to hug random people and dress up like Robert Smith. Go see her new show Trying Is Good (Pleasance Courtyard, 7.15pm) to see if she can pull it off for a second year.

4 Beware gimmicks If Adam Smith arose from his Canongate grave and tookawalkaroundtheFringehive,hewould probably be impressed by some of the technological innovations employed by comedians to gain a competitive edge. But would he laugh? Some acts use a gimmicky premise well: Alex Horne's love of PowerPoint presentation is incongruously funny (Alex Horne: Birdwatching, Pleasance Courtyard, 7.40pm). But the twist in the show is often there to mask some really weak material. Last year, a show promised I would relive the thrill of the Back To The Future films. Instead I just wanted to hop in a DeLorean, travel back in time and warn the comedian: "We've got to do something about your jokes!" The gimmickry isn't just confined to acts; in 2006, the Perrier award was clumsily rebranded as the if.comeddies, to make accountants appear hip and funny.

5 Daniel Kitson is like Arthur's Seat He won the Perrier in 2002 and ever since has acted as if it was the worst thing that's ever happened to him. ButKitsonhasalsobeenthemostintelligent, melancholic and uncompromising comedian in the UK for the past five years. You will never see his face on the side of a taxi, but in terms of quality of material, the most romantic misanthrope on the Fringe stands apart from everyone else, every year. That'swhyhe'slikeArthur'sSeat:untamed, towering above all others, and could usually do with a bit of a prune. (His new show, It's The Fireworks Talking, is at the Stand 1, 11.30pm). Kitsoniscloselyfollowedintheconsistently brilliant stakes by Stewart Lee (41st Best Stand-Up Ever, Udderbelly, 7.30pm).