Not specific to all grain, but
1) Fermentation temperature, generally keeping temps at the very low end of the yeast's recommended temp range.
2) Upper end of recommended pitch rate. Since you're gonna be fermenting on the cold side this is especially important.
3) Good aeration, preferably with pure O2. Again, important since you're going to be fermenting on the cool side of the yeast's recommended temp range.
Mash temp, meh, get it between the goalposts and you're gonna be fine.
Mash pH is an issue if it's an issue. If you're having problems with efficiency or there are pH related flavor issues then worry about mash pH. If not, which will be the case most of the time, then it's not an issue.
Water chemistry is a great way to fine tune the flavors of your beer. If your IPAs don't pop or your lagers aren't as clean as you'd like, water chemistry might be the key. But if your IPAs do pop, well then you probably have good water chemistry for that type of beer and don't need to mess with it.
For something very specific to all grain brewing, the crush, it has a major impact on your efficiency. The finer the crush the higher the efficiency...right up until it's too fine and you get a stuck sparge.