1. No proper names (The first Boggle board spelled out Bryan Drew McMillan.)
2. Must be 4 letter words or more.
3. You may not use the same letter twice, unless there are 2 of those letters on the board.
Since then I've had to add...
4. Must be appropriate words for school. (This one was added after I graded about a dozen "fart" papers in one week. That same week I also got "porn" and "naked". I spoke to my "porn" star, and he was just using a pattern. He honestly didn't know what the word meant. I chose to believe him.)
Each week, I put up the same letters on the bulletin board as their homework.
Sensing a lack of enthusiasm for Boggle, I came up with the idea of adding a little competition. Since, I teach two classes, this was easy. Now, they are trying to come up with the "Longest Boggle word", the "Most Unique Boggle word", and the "Boggle word with the Most Vowels". After I determined the "winners", I had them write their word on a sentence strip and hang it on the wall of honor.
I use Mrs. Rojas' from Create*Teach*Share Boggle printable for homework and her letters for the bulletin board.