What if someone uses a word in Boggle and your Boggle group can't decide if it's acceptable? What criteria can be used to decide if a word is valid for Boggle?
First and foremost, I would recommend having a dictionary handy when playing Boggle. It is a simple way to solve Boggle word disputes. If you don't have a dictionary handy while playing Boggle, or if the dictionary isn't enough to decide if a word is valid for Boggle, I would suggest having all Boggle players take a vote. Do keep in mind when voting that if you decide one player's slang term (for example) is invalid for Boggle, your future slang word will probably be voted down too!
Should I buy Big Boggle (with a square board five letters across) or regular Boggle (with a board four letters across)?
Personally, I prefer the traditional Boggle board with four letters across because I think it forces you to think past the three (and four) letter words more quickly. With the traditional Boggle board you have less total letters and therefore less three-letter words to jot down before taking the time to seek out longer (more interesting and higher point value) Boggle words. In the case of Big Boggle, there are so many more short Boggle words that you're likely to run out of time before getting to search for longer Boggle words (which I find more satisfying). On the other hand, if you have younger Boggle players, Big Boggle provides more opportunity to find a greater number of shorter Boggle words. Additionally, Big Boggle can provide a change of pace for Boggle players who are used to playing traditional Boggle.
Aside from Boggle, are there any other fun word games you could recommend?
Boggle is definitely my favorite word game (as you might guess based on the existence of this Boggle website!), but there are a few other word games I enjoy besides Boggle. Scrabble, for instance, is a classic word game. I would also recommend Taboo. You may not consider Taboo to be a word game (and it isn't as strictly a "word game" as Boggle is), but it challenges players to stretch their vocabulary and thinking beyond the scope of normal, everyday words.