If I put a deposit down on a tent & chairs for a wedding, and now no longer need them, can I get my deposit back?

That depends on what your (oral) agreement was - whether the deposit was non-refundable or not, or refundable only upon notice given within a certain period of time.  If you did not discuss that issue, it may depend on what the custom is in the industry.  You could sue, but that would take time, and you might well lose.  A judge or jury trying to decide what your agreement was will probably ask what would be the point of a deposit if it is refundable under any conditions? Your most efficient (in both time and cost) is to try to work out a compromise with the other side, but if he/she/it will not agree, you will have little option but to sue.