How To: Efficiently Cracking
I've seen way to many people asking how to crack faster.
Here's some simple advice:
Run more than one cracker

See that progress bar? Now I left to get some water and came back about one minute later and here's a nice sight:

See that progress bar? See how it progressed so much faster?
Why does this work better than throwing everything in one? It works better because the more you add, it doesn't add time linearly. It adds in as if it were X^2. What I've done here is cut two usernames / proxy lists in two so they could crack as if it were (X^2) + (X^2) which obviously will move much faster.
Only a few mins later:
Split lists in sections

See how I have 4 lists instead of one? As mentioned in point 1, if I run 4 crackers with 4 lists, the speed increases exponentially, meaning I can go through lists like a knife through butter.
After only 4 minutes, both of my crackers (set to 40 threads) searched through 1000+ each. Instead of one cracker searching and getting only the one 1000+, I've gotten 4 1000+'s. I quadrupled my speed easily.
While this is manly focused on accounts, you can easily do this for password lists and proxies (but then you would need to run more crackers).
As long as your machine can handle it, it would be a good idea to have about 100 accounts per file. If your password list is larger than 30 lines though, you may want to have your files in intervals of something lower such as 50.
Close out of unnecessary processes.
Lowering your CPU usage by closing out of useless processes usually speed up crackers by a tiny bit, more so for slower machines. This CPU that you spared can be spent on using more crackers at the same time to further increase efficiency.
Be sure you are using a trustworthy program
Sure your cracker may work. But is it doing anything odd? Is it running suspiciously slow or is it just repeating the same things over and over in a weird pattern? Scan your system. There have been known crackers that concealed viruses in the past. If you know what language the program is in, try to decompile it. Look if it connects to any externals servers other than the ones it should be connecting to (IE: Minecraft.net = Good while xxs113.net would be suspicious as fuck)
To decompile java programs, use JD-Gui or another well known decompiler such as FernFlower.
For VB or VB.net use IL-SPY.
For any other languages, search Google for appropriate language decompilers.