do i need to clean my phone before putting a screen protector if i havent removed it from the start?

[AC Question]

i got nexus 4 and it came with a screen protector/sticker on it (with the plus/minus and power butten little icons) and i just got a new glass screen protector, so when i remove the screen protector on my phone (for the first time in all the time i have this phone) should i clean it or is it better sticking it quickly without touching it?