I know that I need to cover exposed cords for my lamps, but what else do I need to glider proof?

How should I glider-proof my spare bedroom?

Should I cut out cardboard so they can't get under my dresser and bed?

What about book shelves?

How do you glider-proof a bookcase?

My doors have really big gaps underneath them for air circulation. Do I need to block those?

What about airvents? Should I cover the airvents while they're playing?

Honestly, I got so tired of worrying when I would take them out in my bedroom. I spent so much time gliderproofing and I still couldn't relax and enjoy playtime. I finally caved and ordered a pop up tent (it's mostly screen - Genji $40 - opens & folds down quickly).
It is so much easier and I don't have to worry - it also forces them to interact with you:)

These videos give a great overview:
How to Glider-Proof a Room
Free Range Glider Rules

The tent renee14150 mentioned is the same one i have, i think, and i do like it, but there is so much more fun to be had for them in a whole glider-proofed room.

Mine play under my bed and Zoey has even figured out that she can get into my dresser from behind so she snuggles down into my sweaters. There's nothing that can hurt her so I don't mind.

I don't cover my vents but I do make sure that my windows are closed when they are in there cuz they can bite thru the screen.

Make sure there are no holes in walls or baseboards that they can get in or behind. Other than that I just watch them and see where they climb, if it's a bit precarious, I move it...such as the doilie (sp?) I had draped over my standing jewelry box with a nice heavy incense burner sitting in the center. None of mine ever messed with it, but when I got Ariana, the little booger jumped from my bed to the jewelry box and of course grasped the edge of the doilie so the whole thing came down! Luckily the incense burner didn't land on her cuz it would have squished her! It no longer is there.

No candles, no elec. Sentsy type burners...no medications or candy laying around on table/dresser tops.

Yeah, I'm a worry wart lol

Basically, it is like baby proofing a home! lol Yes, you would want to put something under the doors so they can't get out. If you are supervising playtime in the room, then I would just keep an eye out. Like J&Z said, no candles, no incense, etc. Mine started chewing on the furniture, so just watch out, because they can try to be little destructive buggers.

Honestly I just take sniffles out and she stays on me most of the time, but when she crawls to my hand I know she's about to jump or look. If it's something dangerous I put my hand near my shoulder and she jumps right back on.

I kinda just gave up with proofing other than vents and windows

We don't have space for a tent, wish we did, so I glider proof my bathroom this way: Remove exposed soap and sharp objects s/a razors, keep toilet lid down, cover or close drains, and cover opening of baseboard heater. The baseboard heater was originally covered with a towel, but I found that was not secure and I sat in front of i, making sure it stayed covered and so could not really relax. For a temporary solution I added the magnet tape to a strip of fleece big enough to cover the opening and secure with magnet, I showed my husband how I would like some heat/resistant mesh sized and bent that can fit over the opening and secured with magnet, so when winter comes around I can still have heat without danger to my girls. My bathroom is small, but still a fairly large space for the girls, they love to run up my bathrobe hanging on the door and jump to my towels on towel bar and back. Skadoosh seems more adventurous and usually begins the activities soon after we settle in, sometimes she'll jump to the shower curtain rod and run back and forth a couple of times. Lulu usually hangs around me and the floor close by, then will venture to the robe and towel bar. I do not have a window in bath, so I learned to keep light off and use a battery operated lamp on low sitting on the floor, keeps it dim for them, and I can see what they're up to.