Make sure it's dry and give it a good clean with some alcohol wipes.

A hairdryer might help by heating the plastic then putting the stickers on so they stick really well ?

Someone I know did this to his front wing. He stuck the stickers on then lightly laqured over the top.

i have stickerbombed the centre console and rear view mirror in mine looks mint il post some photos up when i get back off hol but thats not till next week. The link with the set off ebay is very good, thats what i used as its alot easier to get that off than random stickers. I also did one of my steels as a laff for the shark stand at GTi inters il post pictures up but it definitly looks good in moderation

I'm only going to do the splitter then prehaps my spoiler (splitter first) going to start tomorrow just got car back from the paint shop I'll post my pics up in a new thread tommorow!