I can't tell you how many questions I get via email concerning crimp beads - tons! In fact, that is one reason I have so many article about them on this site:
You would think I had covered it all, but seriously, there are so many issues with crimp beads I could probably write a book about them.
Beginners, especially, have a heck of a time figuring them out.
So, along with all the information I've already provided about these little findings with the big issues, the other bead crimp issue I get asked about a lot concerns which size crimp bead to use with which size beading wire. Before I jump into this, I'm going to give a disclaimer: honestly the answer depends on a lot of variables and each manufacturer of beading wire (Soft Flex, Beadalon, and Accuflex) each has guidelines they offer for each size of beading wire. So, if you want detailed specifics, go to the corresponding manufacturer's web site for more information. However, if you want a basic answer, here you go:
*For most beads under 4mm as well as small pearls, I suggest using .010 to .012 beading wire and 1x1mm crimp beads.
*For most beads in the 4 to 8mm range, possibly even 10mm depending on bead weight, I suggest using .014 or .015 beading wire and 2x2mm crimp beads.
*For most beads in the 10mm and up range, I suggest using .019 to .024 beading wire and 3x3mm crimp beads.
Also, make sure you use the correct crimping pliers for each crimp bead:
1x1mm crimp beads should be used with micro crimpers
2x2mm crimp beads should be used with normal crimp pliers
3x3mm crimp beads should be used with mighty crimp pliers.
These are really general guidelines. As I said before, there are so many variables (bead size, length of jewelry piece, weight of beads, etc) that there is no clear cut "one" answer to fit all bead stringing situations.