I use a RedRock 512 electronic caller with Jonny Stewart Cassete tapes.
It's a nice handy lil package that works!
I normally use it with a spot light and a cottontail wiggle decoy at night or late evening.
Let the tape play and periodically light up the area look for eyes glowing.
I started with mouth calls but I have found that this set up works better for me. I have a open reed howler there is a curve to learning how to use them But once you get the hang of it they are effective. I also have closed reed calls that I have used in the past with success. Tapes or MP3s are about the easiest way to go tho.... One thing I have noticed is if you don't switch up calls/tapes (sounds) after you shoot acouple off of a spot they seem to recognize said call as danger and won't come as close. Or so it seems....