Does anybody have a primer on pickpocketing? It's the one skill that I don't have a good handle on.
Here's some assumptions I'm making:
Since you have to go into Sneak mode to pp, then the 2 are tied together; if you're detected, then pp is much more difficult.
It's easier to pickpocket from behind
It's easier to pickpocket at night.

Am I on the right track? Also, if I pp when other people are around, am I more likely to get caught (by others, if not the vic) than if they're alone?

I am wondering this myself. I'm hidden when I pickpocket, and the tooltip says "90%" chance, but it seems like I get caught 3/5 times at best. I find it really hard not to abuse the quicksave feature...

yes, a high sneak skill helps. you can also find enchanted items and potions that boost pickpocketing and make it a bit easier. the more you do it, the more it levels up and the easier it becomes. just keep at it.

F5 just before you pickpocket each time. If you get caught, F9 and retry.

But, yes, make sure you are not seen in sneak mode. From behind is best. You can get a perk that helps when they are sleeping.

enchant some gear
fast travel to the big towns, put muffle on your boots,
steal the expensive gems/ jewls
i lvled it fro 30 to 100 in like 45 min and make money to save and never buy any thing because i make stuff
fill out the tree to get the extra 100 weight
easy breazy
after a while i could steal stuff while they where looking right at me with the eye wide open
funny
dont reverse takes forever no weaponds the more expensive the more exp

Yes pickpocket relies a lot on sneak. I think your odds to steal are halved when you are detected. (Not sure)

To train your pickpocket skill, go to houses at night and practice on the sleeping people. Even with 15-20 in pickpocket and no perks, you have about 40% to succeed with light stuff (gold, food, potions) and you need to steal only 2 or 3 items to level up your skill.
The annoying part is that when you fail, you get a bounty or you reload.

I have not noticed anything about it behind harded at night or from behind. (although remaining hidden is definitely easier from behind)

You gain the skill quickly if you steal things that are more valuable. The five hundred dollar necklace will boost you quite a bit. So, practice on rich people, but don't take unnecessary longshots.