• Wear a cycling cap under the helmet, peak forward over the eye's.
• Shades with clear or yellow lenses.
• Rub leg goop or baby oil over the knees, to shed water and keep these vital moving parts warmer.
• Give yourself a little more space, especially at corners and downhill's.
• Decrease use of front brake.
• Extra lube on chain and transmission.
• Make sure tires are inflated, you don't want to aquaplane.
• Plastic bag up inside of jersey, or wear a racing rain jacket.

Don't worry too much about your tires. You can't really aquaplane on narrow road bike tires so the tread pattern is really a comfort thing. I used to race crits on Michelin slicks no matter what the weather. You should run your tires a bit softer than normal just to increase the contact patch. I risked pressures as low as 80PSI in particularly nasty conditions. You can always wash your tires with mild detergent (washing up liquid) before the race to get a bit of the newness out of them.

Try to get all your braking done in a straight line and avoid metal grids and white lines. Avoid big puddles, as you never know what they may hide.

Never give up in a wet race as it is really surprising how many people get fed up and drop out. Punctures seem to be more prevalent in wet conditions.

Yellow lenses rule in low light rain situations but do yourself a favor and use "rain X" on your lenses (WARNING: Don't try this on Iridium's or anything too expensive). I can vouch that Bolle lenses do not melt when "rain X" is applied :-)

Put something waterproof and windproof (e.g. a shopping bag) down the front of your jersey if it is cold and wet.

Baby oil on your legs and lightweight over-shoes increase your general comfort on the bike.

Have fun!

It seems there maybe a difference of opinion regarding tire pressure. I got my advice from Richard Hallet, the technical adviser on the British publication "Cycling weekly". I do agree that tread is pretty much irrelavent. I ride a whole season in England on Specialized Turbo R's, the treadles 20mm tire. I had one crash due to wheels slipping, but the rest of the field came down as well, so I do not think you could blame the lack of squiggles on the tire.

Don't use coloured (non-black) tyres!

An additive to the rubber in tyres which makes them impossible to be anything other than black is "carbon black". This makes the tyre much more grippy in wet conditions than, say, a purely silca-based tyre. This is the reason why automotive tyres are still black: coloured tyres have been around for a long time, but do not work as well as black tyres.

A personal anecdote: Racing in Scotland in wet conditions in one of the early groups in a pursuit race. I was the only rider not on coloured tyres in the group, and was the only rider who was not sliding their rear wheel round corners!