How do you go about determining what an "acceptable" amount of fret buzz is? My low e string on my Ibanez RG3 buzzes on a number of different frets, despite having my action set a mile high. If I pick the low e string fairly agressively I'll get the fret buzz. On my MIM strat the action is a lot lower, and I noticed that the fret buzz is even more common, yet is much less audible. I recently started taking lessons and my instructor commented that I need a truss rod adjustment to bring the neck back down. I made an adjustment, but because it brought my strings down closer to the fretboard, my buzz was much worse, so I set the neck back how it was with my mile high action. My other 5 strings don't buzz, nor did they when I adjusted the truss rod.

I've run a straight-edge over my frets, and other than a slightly concave profile down the fretboard, the frets seem to be even.

Should the truss rod adjustment only change the concave profile of the fretboard, or will it change the profile of the whole neck, which in turn changes the string height over the last fret? Is some buzz just to be expected on the low e string? Maybe I'm picking it too hard?
You should never have fret buzz. It will kill your sustain and its quite irritating.
Do you have a floyd rose bridge? If so you might have to adjust the height on one side of the guitar to get rid of it. Or you can take it to a good guitar shop to have it set up.
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The Ibanez is a fixed bridge, the strat has your standard issue mexican strat trem. I've raised the action on the e string on the Ibanez already, but like I said, my action is already a mile high. My strings sit nearly 1/4" above my last fret.

Rather than just take it to a shop, I want to learn how to set it up myself.
Anybody else ever encounter this situation and have the know-how to fix it themselves?
jst for an idea for rock playing string height, an ideal setting should be about 0.013 of an inch or 0.33mm ish between the bottom of the low E string and the top of the 7th fret. This is how i have mine set up and it gives minimum buzz and a great tone. If you wanna play decent pace rock you need to accept a slight buzzing as long as it doesn't make ur tone and sustain awful. To measure i use my nut files which are set widths so its easy to set string height with them, check on ebay.
things tht could be wrong with the guitar could be dodgey or worn frets, the nut being worn or at the wrong height, or ur guitar may need a truss rod adjustment which affects the curve of the neck. take it to a guitar shop if you don't know what ur doing cos you could permanently brake ur guitar.
Thicker strings will also reduce buzz at a low action as they are pulled tighter to get the correct tuning. Its worth the higher gauge strings for the tone and it strenghtens ur fingers, although it might be hard to begin with.
Last night I talked to a local guitar shop to try and learn. "Take it to a shop" isn't going to ever help me learn anything, and I'm not the type who's interested in paying other people to make simple adjustments that I can do myself. The guy at the shop said that the relief in my neck should be barely noticable to the eye when looking down the neck. Mine is clearly noticable, and when I fret the low e on the 1st and last fret, I had somewhere around 1-1.5mm of relief on the 7th fret. I adjusted the truss rod a tad and now my neck is almost perfectly straight, with an ever so slight relief. I re-adjusted my action after making my truss rod adjustment. My action is still a mile high, but my fret buzz seems to be much improved unless I really crank on the string. As my picking & strumming improves so that I'm not hammering on the strings I think I'll be able to come down on the action.

I really don't think that you're going to ruin anything by attempting these adjustments yourself unless you do something incredibly stupid like cranking the truss rod a mile too far. I made about a 1/4 turn on the rod and saw an immediate improvement, and rather than going farther, I let the neck acclimate to the new pressure. By this morning a bit more relief had come out and it's unlikely that I'll need to make any additional adjustments.