I was wondering if anyone could help me decide which levels it would be best to take these perks specifically:

Level 2 – Rapid Reload
Level 4 – Comprehension
Level 6 – Commando
Level 8 – Old World Gourmet
Level 10 – Scrounger
Level 12 – Shotgun Surgeon
Level 14 – Entomologist
Level 16 – Weapon Handling
Level 18 – Travel Light
Level 20 – Hand Loader
Level 22 – Pack Rat
Level 24 – Jury Rigging
Level 26 – Long Haul
Level 28 – Quick Draw
Level 30 – Rad Child
Level 32 – Toughness
Level 34 – Toughness

I've already decided which perks I want, obviously. I just want to know when I should take which perk.

Thanks for any help

I would get Rad Child as early as possible - about the time you hit Novac if you follow the long route about. It's so insanely powerful that almost feels like cheating, even with the least rad sickness.
You can find three of the survival books by that time, and the fourth soon after, before you reach Vegas.

Okay, I worked things around a little, and I think this order works a bit better:

Level 2 – Rapid Reload
Level 4 – Comprehension
Level 6 – Commando
Level 8 – Old World Gourmet
Level 10 – Rad Child
Level 12 – Shotgun Surgeon
Level 14 – Travel Light
Level 16 – Weapon Handling
Level 18 – Hand Loader
Level 20 – Pack Rat
Level 22 – Entomologist
Level 24 – Jury Rigging
Level 26 – Long Haul
Level 28 – Toughness
Level 30 – Toughness
Level 32 – Quick Draw
Level 34 – And Stay Back

I scrapped Scrounger in place of And Stay Back (just for a fun last perk) because I read that Scrounger isn't really worthwhile, especially with Hand Loader. And I placed Rad Child much earlier thanks to Fleapants' advice.