I find myself soldering leads to switches, potentiometers, jacks, etc so I can use them on a breadboard. Their "legs" are too large, too short, or does not match the breadboard hole spacing.
How do I specify that I want breadboard compatible parts when I search in Octopart, Digikey, etc?
Thank you in advance.
For switches and pots "through hole" is probably one term you should look for.
For IC's you want DIP.
Also, the parts should have a "pitch" or spaceing between the leads of .1" or around 2.5mm.
You might consider looking at the data sheets for the parts as well. Those often contain drawings of the part in question.
These are becoming harder to find these days and you will tend to spend more on them.
The solution is to look out for break out boards and adaptors. Sadly that makes it more expensive as well. 
trimpots will fit a breadboard and so will most microswitches
usually their leads have a little zig-zag bend in them, which makes them shorter and want to pop out, but I usually flatten those with a pair of needle nose pliers and they work great
Shopping for parts in the surplus market will often turn up items that are not only (more) breadboard-compatible, but also cheaper.
There aren't many jacks of any sort that are breadboard-friendly. What I've been doing lately is putting breadboards on old Lego baseplates, and mounting parts like jacks and pots to Lego plates and brackets with soldered-on leads to connect them electrically. That gives me relatively sturdy mechanical connections, with flexible positioning and less use of breadboard space.