others will give advice which stuff is best for protection, but one basic rule.
Do NOT use washing-up liquid to wash the bike, we've discussed it before but basically it contains salts and stuff that just make corrosion worse.
Use a decent car body shampoo from your favourite accessory store. My preference is for Autoglym Bodywork Shampoo, but most are fine.
Also the Autoglym Vinyl&Rubber Care stuff is good for plastics and spraying onto just washed engines etc (it recommends it on the bottle).
If you want heavy duty protection
![Shocked](images/smilies/icon_eek.gif)
then Waxoyl does the trick, but it looks grubby. It's quite easily cleaned off in Spring with a spray of WD40 and a rag.