Now if you have really large limes, I sometimes reduce the limes... but in general if I pick up two avocados, I pick up two limes. If I choose 4 avocados, I use 4 limes... so on and so forth.
I make it in a bowl with a fork or sometimes I throw it into my food processor (especially if my avocados are a bit firmer).
I only make up enough for what we will eat in one sitting. It is too easy to whip together not to always have fresh.