(This works best for characters who plan on using archery a lot)

With a little bit of gold (I had about 1000 or so) speak to Faendal (he must be a follower and be following you) and get him to train you in archery, spend all your money on this. Afterwards, exit the training box and trade items with him. All the spent gold will be in his inventory, so just take it out and it will go back to your inventory. Now just start training in archery again, and continue doing this. Every so often you'll need to exit and level up though.

You can only do this for so long however, as I lost the dialogue option to be trained by him.

I am sure you can do this with any follower who is also a trainer.

I'm pretty sure everyone knows about this

but if not, they do now!

Figured as much.

I thought I was the first.

yeah. I do that trick with any trainer that can be a follower. The companions for example almost every one in there will train you for something.

Another neat trick is to buy say one perk from a trainer who can't be a follower. And then steal the money back. Two perks for the price of none haha. Pickpocket and what ever it was you trained for in the first place. Start out buying only one perk. You'll get caught every time trying to steal back say... 16000 gold.