Already been mentioned about those first few minutes after the rain starts, esp if it's not rained in a while... watch your footing at stoplights, planting a foot on a little oil on top of a little water can induce a little pucker factor.
Try to keep your glasses as clean as possible, I always flip down my visor on my helmet. Then move my head sideways left and right when carrying a bit of speed to get those water drops off. It works pretty well starting from around 30 mph to clear the rain.
Ow, watch out for sewer covers (amongst others), they are scary slippery.
I rode my bike for the first time in the rain. It seem to handle okay and the only bad thing was the build-up of water on my glasses. Any tips to riding in the rain? I am kind of new to this.
Yea, riding in the rain just blows, I don't know anyone who enjoys it. Beside the other suggestions mentioned, I would make myself as visible as possible to the others drivers on the road. Wear a high visibility vest or at least reflective piping of sorts on your foul weather gear, you are not the only vehicle having a hard time seeing. If the weather is too bad I will pull over somewhere and wait it out.
Lost of good suggestions here, but rain riding is not nearly as bad as some would have you believe. Just be alert, slow down and ride carefully like these guys: