My tips would be:
1 - Choose keywords carefully - notice the any, all and phrase switch. It only sees words. Do not use quotes, +, -, AND, NOT... Use the pulldown switch.
2 - By user: can be blank - notice another switch - "Any poster" works if you don't care who wrote it. 'Started' and 'posted in' both require a name. (I think)
3 - Select only the relevant board(s) to your search.
4 - Start by unchecking message for a faster search.
5 - Age depends on what you're looking for.

Try searching for this thread, then this post only, the beginning post... using the same couple of keywords. See what the switches do. The goal of searching is not a huge quantity of results. It's a few good results.

It's been reeealy slooow since the move. The less boards and text you ask it to search the faster it goes.