Here are some tips and tricks I have learned along the way:
Watch fashion magazines closely - Cosmopolitan, InStyle, and Glamour just to name a few. The hot colors and looks of the season impact the event industry.
Buy wholesale. There are many companies on the Internet that allow individuals to buy products at wholesale prices.
Check restaurant supply stores. You can find some great things like shot glasses, utensils, beverage dispensers and more.
Are you on a tight budget, but aren't comfortable asking for guests to bring their own beverage or food? Ask some close friends that you are inviting to contribute. Most will be happy to help. Or, have a contest on food items that guests bring like most original, best tasting, and most attractive.
Be careful about postage charges. It is really embarrassing to send out a great invitation and then learn your guests had to pay the difference in postage.