Rinse the yeast. If you haven't purchased Yeast: The Practical Guide to Beer Fermentation
by Chris White then get yourself over to Amazon and pick up a copy. It's invaluable.
To rinse the yeast, sterilize some water and let it cool to room temperature. Pour the water into your sample of trub/yeast/gunk to dilute it. Stir it and let it settle. After an hour or two, it should settle into three layers:
- Mostly transparent top layer (consisting of proteins, lipids, etc.)
- Milky center layer (live yeast)
- Dirty bottom layer (trub, dead yeast cells, hop particles)
Pour off the top and discard. Decant the middle layer (this is your yeast). Discard the bottom layer. I use a 2L flask.