If we're talking about refinancing a mortgage, make sure you know everything about your current mortgage. Know your interest rate and compare it to the lenders' offer.
Research: Before diving in it would be essential to gather as many information as possible: application fees, mortgage break fees and other related fees. Don't be afraid to ask.
Look at the big picture. Don't get stuck within individual fees and percentages. Figure out the best overall deal, the one that will get results on the long run.
Find a good independent mortgage adviser who can guide you at every step of the process and lift the pressure of your shoulders, and review the offer regularly.