Here's what I've done:
*Chill the can or bottle at least overnight. This will help compact most of the the yeast at the bottom so you can keep it on the bottom as you pour out the beer.
*Make starter and cool (see table below for step sizes I used).
*Slowly pour the beer into a glass leaving some beer/yeast in the bottle/can.
*Swirl the can/bottle and pour the remaining liquid into your starter and aerate.
*Loosely cover and place in a warm location.
*Shake intermittently, I do not use a stir plate on my first two steps to keep growth rates controlled. *Depending on the age of the yeast, it could take anywhere from 1 to 4 days for you to see any signs of fermentation. If you don't see anything after 4 days, raise the temp to 70-75 degrees, shake hard, and let it sit 24 hours. At that point, the yeast usually kicks into action and you might see some yeast rafts in the middle of the wort and a tiny bit of krausen. If you still don't see anything, try proceeding to the next step anyway.
*Repeat steps making bigger and bigger starter to grow the yeast to a pitchable quantity.
*Let each step ferment for 2 days.
*If you have a big enough container, you can pour the current step into the next step (this is preferred).
*If you get to a size where you can't do that, chill your starter in the fridge for 2 days. Remove from fridge and decant the clear liquid on the top leaving a little behind. Swirl the container to get the yeast into suspension and all to warm up to the temp of the next step and then pitch that.
Here are the step sizes I used:
