Scottie, when you say you got a stirrer do you mean a stir plate? I am guessing you want to make a yeast starter? Remember, this is for liquid yeast. Dry yeast is simply re-hydrated like a wine yeast.
Ok, depending on how big a starter you want take a pint of water to 1/2 cup DME ratio. If you want a bigger starter increase as needed. That ratio will give you around a 1.040 gravity. You can do it a couple different ways. I have large Pyrex flasks I do my starters in that I can boil the starter right on the stove in the flask. This sanitizes the flask as I boil.
If you don't have a flask and are using a jar for example, boil the wort in a pan on the stove for 10 minutes and pour into a sanitized container. Add 1/4 tsp of yeast nutrient. Cover the jar with some aluminum foil. Don't boil too long or you will boil away too much water and have too high a gravity for the starter.
Set the jar in the sink with some cool water in it to cool the wort. You want the wort and your yeast vial or slap pack about the same temp. Remember to take your vial or slap pack out of the fridge the day before.
When the wort is cooled add the yeast and place the foil back over the opening of the the container. Don't forget to add your sanitized stir bar. Set the container on the stir plate and turn it on. If the stir plate is adjustable speed, set the speed till you see the vortex.
The strain used and the size of the starter will reflect the time to stir the starter. I normally do mine for a day to two days. I normally decant the liquid of the yeast bed and add the slurry to the beer. Most beers though you can just dump it all in.
Hope this helps. Here is a pic of an English Ale yeast strain. Notice the large flocculation. I let this settle after it was done and pitched the slurry in a stout. Many strains you won't see the yeast so prominent while it is stirring.
