Reverse Engineering

.Net

If dealing with a .net binary then the easiest way to decompile is to use dotPeek. This can decompile and then export the decompiled binary as a project, making it incredibly easy to debug and work out behaviour. Of course this is assuming no obfuscation has taken place.

Classic C Binaries

ltrace

This will show all function calls made by a program.

strace

This will show all syscalls made by a program.