When laminating, whether you're using a cold seal or heat, or even if you're using the peel and stick sheets you can buy at your local office supply store, the real key is making sure your document is clean. You will be incredibly disappointed if you go through all the trouble of laminating, only to realize there's a big hair stretching across half your document. So, clean everything off and laminate as soon as possible after the cleaning.
If you're laminating using a machine, follow all the instructions that come with the machine, to ensure that you don't end up with trapped air under the surface. When doing the lamination with the peel and stick method, this will be a more difficult task. Start from one end of the document, and slowly press the sticky sheet and your document together. Use the flat edge of something (like a credit card) to help you attach the two items. When you are finished, if there are air bubbles, you can use the credit card to attempt to push out the air. But be careful that you don't use something that will accidentally cut through the plastic.
If you do cut the plastic, or you need to redo the lamination for some reason, you could be in trouble. If you only have one copy of this document, scan it (or take a picture) before you attempt any removal of the lamination; that way you'll at least have some record of the document. If you're able to find an area where the laminate plastic and the document meet, you could try to make a seam in that area. If you're successful, you can slowly pull the plastic away from the document. You might need to add heat in order to soften the plastic laminate. But if you realize that the plastic is simply not going to pull away without damaging the document, it's best to stop and just use what you have.