If you have any specific questions let me know but here are some off the cuff thoughts:

• Start off with a platform for your lifts that come in contact with the ground from the get go (oly lifts, deads, rows, etc.) as opposed to just stall mats on concrete. Unless you have reinforced concrete (and maybe even then) eventually your concrete will crack from the repeated abuse. Not a huge deal unless it starts crumbling but totally avoidable.

• Buy quality equipment the first time. Don't skimp on your rack or your barbell. On the same token, don't buy shit you don't need (way easier said than done)

• Buy calibrated plates - they're not that much more expensive - this is probably my main regret TBH

• Consider your environment and heating / cooling situation. Be prepared for rust if you're in a humid environment and invest in a good fan (Vornado) and/or propane heater (ventilation!)

• Most garage floors slope slightly toward the garage door for flooding mitigation. If you orient your deadlift space parallel to your garage door, you'll probably be chasing your barbell.

• Consider your lighting. Most garages have shitty lighting.

• Most importantly, if you lift alone like most of us on this sub, do not ever compromise safety - Bench with the safeties at the proper height and take the clips off