Which lunar phase comes directly before the full moon phase

Waxing Gibbous is your answer, but lemme run you through anyways (simply because this is one of the most interesting things to me.)
So you have a New Moon, no light at all.
Then from there to half coverage is the Waxing Crescent. 
AT the half coverage is the First Quarter.
Then from the half to full coverage is the Waxing Gibbous. (your answer)
Then comes the Full Moon. 
And now begins the descent backwards IN to New moon.
Waning Gibbous is after full moon, which represents the decreasing visible moon to what we call the Last Quarter. Which is the last half moon visible. Then The Waning Crescent. Which is from the Last Quarter to-yes you guessed it-a New Moon. 
Now in case you didn't catch the pattern, Waxing is the seen visibility from left to right (up to the halfway mark also known as the First Quarter. Then it goes into waxing again.) So new up to half is Waxing Crescent. Half is First quarter. Waxing Gibbous. Full moon. Make Sense? But now you just go backwards and put Waning/Last in front of the names. (Gibbous being the most moon visible without going full and Crescent being the least without half.) It's not as hard as you think, I promise :)

Probably a behavioral adaptation