You want a clean, dry surface. If you're starting with that, a quick wipe down with some denatured alcohol - even rubbing (isopropyl) alcohol will do - to be sure the surface is grease and oil free.
When I'm starting with a really fouled up surface I start a water based cleaner . Something like Simple Green. Maybe a citrus cleaner. I had a floor once that was so bad that I had to start with a scraper - an old ice scraper worked really well. Once the surface is clean, I finish with the alcohol wipe down.
Please Use a Roller!
CLD Tiles™ don't need a lot of pressure but you don't want to slide your hands along the edges to apply it. The 8 mil foil can be very sharp. It will cut your flesh. Use a roller, a jar, a 2x4 - anything but your hand. A roller is free with the purchase of 60 or more CLD tiles™.
All you need to do is make sure there are no air bubbles between the adhesive and panel. Pressing too hard risks deforming the panel and curling the foil away from the adhesive. Easy does it.
Distribution on a Panel
The rule of thumb is: enough CLD Tile™ to cover 25% of the surface distributed over the central 50%-75% of the panel.