a little help repitching yeast

my batch is sitting in its secondary fermentation right now, and in about a week I am going to start botteling . I was wondering how big should the yeast cake be to make it worth saving and what is the best method to save the yeast?

It's best to save the yeast out of the primary. The yeast in the secondary is all of the slow ones that didn't get their job done soon enough.

The best method is to use the yeast immediately for another beer so it is fresh and healthy. If you are looking to store the yeast for more than a couple days, search "yeast washing".

https://www.homebrewtalk.com/f13/yeast-washing-illustrated-41768/

awesome thanks for the help. I'll problably just forgo this batch since I've moved passed the primary. and save the yeast from my next batch.

Yeah, the best thing to do is brew the day you plan on racking. For a 5 gallon brew, a cup or so of yeast slurry is plenty. While you are brewing the new beer, rack the other one to secondary or keg or wherever you put it, but save a cup or so in the bottom to swirl the yeast into suspension. Pour off excess yeast, keeping the fermenter sanitized, and then after brewing rack the new beer right on the yeast. Plan on going from lighter to darker in color and lower to stronger in alcohol. You don't want dark yeast from a stout to color your blonde, or the tired yeast from a barleywine to try to ferment your pale ale.

I save the cake in a 2 liter PET refrigerate, pour off the liquid, pour into a smaller pet or bottle in a 330ml glass bottle and cap it. Refrigerate again, if you don't use it for some weeks you will find it will settle to around 100mls or less of yeast and the rest is liquid.
Beware with this method sometimes they blow like champagne when you pop the top.
I usually pop the top (warm it to room temp first) pour off most of the liquid, shake the rest up to suspend the yeast and throw the rest in. Probably 150mls slurry.

I have plenty of success harvesting from the secondary - depends how long you were in your primary for, though. I tend to rack pretty "young", so there's lots of yeast in there. The upside is it's cleaner. IMO.