Buy a some bottle conditioned beer. I find Shepherd Neame Spitfire yeast used to revive well, floculate well and gave good results. Unfortunately, since about 2000 it stopped being bottle conditioned. Let the bottle settle for a few days. About three days before brewing, prepare a starter bottle using either wort from your previous brew or 50 g malt extract in 350 ml water.
Spitfire leaves a really solid yeast deposit at the bottom of the bottle.
Pour some liquid from the starter bottle into the beer bottle, shake around to oxygenate and stir up the sediment, and pour back into the starter bottle. A couple of transfers back and forth between beer bottle and starter bottle help oxygenate the beer further as well as getting any extra bits of yeast out. Put the airlock back into the starter bottle. I find that Spitfire yeast should be going well and ready for pitching after about three days. Drink the beer in the glass.