First thing I would do if I were you is determine how many vehicles you want to park inside the garage when it is all finished! Then design your layout around that.If you are going to do a lot of work in the garage I would also look at a plywood wall covering or siding instead of sheetrock.Personally I am going to use a 4x8 plywood that looks like bead board,my Garage doubles as a game room also and has central A/C and heat.Just a few tips from my experience!
#1.You can get some garage design books that have some really cool ideas and pictures.
#2. Determine how many vehicles you are going to park in the garage and design around that.
#3. Install more than needed electrical outlets and be sure to add a few 220 volt outlets in areas you may use welder or other 220 volt tools etc!
#4.At this point you can install all the piping for the air lines in the wall,I would use galvanized pipe to help cut down on rust from moisture in the piping and install a good filter system and install outlets in strategic areas throughout the garage and maybe even one outside to blow off the mower after use!Do not use PVC or CPVC for airlines!
#5.Insulate well now! You will be glad you did in the future!
#6. Use a good water barrier but be sure to let the garage breathe,install a couple of good vents and if you think you may install A/C use vents you can open and close at your discretion.
#7.Decide on good solid cabinets,Sears makes some really nice ones,they are a little pricey but look great and are durable.
#8.Use good quality durable paint on walls and ceilings Personally i would use a good epoxy paint! and pick a good durable floor coating.Members here have used different types and they can recommend some good ones.
#9. You can also install a fire suspression system in the garage that will automatically discharge in case of a fire.They cost a little bit but not near as much as you will have in the garage and what you keep in there! A very good piece of mind!Or install good fire extinguishers in startegic areas.Or Both!
#10. Just be thoughtful and try to think ahead to minimize mistakes on installing air line outlets,electrical outlets,vents etc. Storage of items you are going to keep in the garage.
#11. The value of your home also depends on the quality of your garage and If you decide to sell later on it makes a good selling point to the MAN OF THE HOUSE! Especially if he is a CAR GUY ALSO!And maybe the LADY of the house also.
#12. You started off right about asking others questions,now get a couple of books and look at some picture of garages and make a few decisions and GET TO WORK! LOL
The better you plan now will make it a lot easier down the road!Don't scrimp on the garage funds you will regret it,you can be frugal and have a fantastic garage too!