I'm considering building a character to do the Thieves Guild and Dark Brotherhood quests (I've gotten about halfway through both in the past, but got sidetracked, so I haven't completed either yet.) and was looking for some tips. At first I tried to play characters designed specifically for each, but I found that playing two stealth characters at the same time didn't work for me. (I only seem to be able to play warriors, thieves, and mages at the same time.)
I know that it's best to do the Thieves Guild first (mainly to be a higher level to get the leveled DB items) and I think it would be interesting to do the Mephala quest to get in the DB. Beyond this, is there anything else I should consider before I go this route?