I like to make encounters with lots of monsters of different types. It’s more fun to work through an army of mooks, having your ranger shut down enemy spellcasters with readied range attacks, sorcerer obliterating tightly packed minions, cleric tanking support bruisers and protecting the flank while the fighter chews into the Big Bad Evil Guy than fighting another behir. However, it can be tough to eyeball the encounter level of a mixed group of monsters.

As a quick check, I like to use the Encounter Calculator. You can quickly see if a given set of monsters is going to be somewhat tough or extremely challenging, and it may save you some frustration at the game table. Encounter levels aren’t an exact science, of course, but I’ve modified encounters a few times with this tool and found the result to be about right for my players.