1. Read the instructions most toilets have installation instructions. But we will do a brief, commentary.
2. When choosing a toilet, and for a more comfortable toilet. I prefer "American Standard Champion 4 Max Tall Height 2 Piece High Efficiency. Elongated toilet.
Or also The Kohler Cimarron "Kohler elongated toilet", both cost 199.00 each at the Home Depot. Rather the a standard round toilet. And since it is just a little bit more comfortable, more bigger, spacious.
3. Take a Measurement from the back wall to center of the holes or rather. Were the screws are protruding from the toilet. You will need a minimum clearance of 11" inches, from back of wall to toilet bolts. (They sell special toilets for when the measurement is less. There called a 10" rough toilet.
4. I, Always prefer to remove the old toilet bolts. And install new toilet bolts, a new wax ring, a new water supply line.
5. If toilet is a two piece, (not a one piece toilet). Install toilet tank to toilet bowl making sure that the toilet tank is set squarely on the toilet bowl.
(By that I mean that toilet is not facing more to the front on one side, then the other side. It's squared.) "Evenly tighten" down on toilet tank bolts to toilet bowl. Then just install toilet bowl seat.
6. When you set the toilet down make sure that toilet doesn't rock "pre-set it on the floor" before you install the wax ring. If the toilet "ROCKS". There is something called "shims" made of plastic.
Usually that is needed, to level out the toilet. Only two or three shims, usually in the front. Make sure the wax ring is a good one. They sale extra thick wax rings (Less Likely to leak). Place a thin line or bead of dap (Water based type dap, easier to clean-up) around the base of the toilet. use a moist rag to wipe excess off.
7. If the Angle stop (Water Shut-off valve) doesn't work. I usually change it because you never know when you have to shut-off the water.
8. Connect A New water supply Line (Water Supply lines have a rubber cone which will compress when installing the first time.) and check for Leaks.
A SAN DIEGO PLUMBER always recommends to let a
professional do the work.