Try modeling the word you are encouraging to the tune of a song. You can either replace every word with the word you are modeling, or most of the words, or occasionally replace words.
An easy song to use is "row, row, row your boat", but you can use more complicated songs as well (especially motivating for older children). I sometimes have fun myself just thinking of different songs that are fun to use to model words to. ("We like to move it, move it" "In the jungle the music jungle, the music sleeps tonight", or "shake, shake, shake, ...shake, shake, shake, shake your arms", or say the word "ride" to the tune of the lone ranger. There are sooo many ways to do this!!!)
I have also seen this work with kids who have echolalia, try singing the phrase that you are modeling (such as "Let's play jumping ghost") then pause and ask them what they want (then the phrase won't be the last thing you said), but they can remember the whole phrase easier!
Have fun rocking out your words!