Step 1. Read/review, understand, and follow..
http://www.aquariacentral.com/forums/showthread.php?t=64301
http://www.aquariacentral.com/forums/showthread.php?t=26051
http://www.aquariacentral.com/forums/showthread.php?t=50188
Step 2. Your first purchase should be a good liquid test kit that handles ammonia, nitrite, nitrate, pH, GH, KH.
Step 3. Find out what your local water supplier uses to treat your water, chlorine or chloramine. You will need to treat your water initially and at each weekly water change. I recommend Prime. Stay away from Cycle.
Step 4. Purchase a good gravel vacuum for your tank cleaning. If possible this should include a Python, especially with an 80 gal tank. YOU WILL NOT BE ABLE TO ADD CHEMICALS TO MAKE YOUR TANK MAINTENANCE FREE AND IGNORE WATER CHANGES.
Step 5. Research your fish that you are interested in, BEFORE purchasing them. Many sites have species profiles and many species have sites dedicated just to that fish. You will need to consider not only their size, but temperament, diet, spawning characteristics, compatibility (and how it changes), habitat and how much space they need or the need for schools for acceptable interaction.
Step 6. Over filtrate. Most filters only deliver half of what they state. On an 80, you probably should have a least the canister and a power head to minmize stagnant areas.
Step 7. Once you have a firm idea of what you want, post here with your stocking plan for useful advice.
Good Luck!
Oh... the coarse pads help filter out larger debri, the fine are to trap the smaller ones.