I'm not a caterer but I am a great marketer. Hopefully, you're past the research phase and have a feel for what a fair, competitive price looks like to your customers and competitors.
Your question is, "what can I do?" The quick answer is--as much as possible. Most entrepreneurs/SB owners fade away because their marketing strategies were weak.
As has been mentioned, word-of-mouth is free and amazing..but it's useless if you have no mouths to spread the word..this marketing weapon will work itself out if you do everything else well.
Satisfied customers > credibility > word-of-mouth > REPUTATION (all FREE)
If you're serious about catering, you'll have to make investments (I didn't say "spend"..I said "invest")
Ways to invest time/money:
1) get involved with your local chamber of commerce...they will do you a lot of good. Networking is important!! and local businesses always scratch each others' backs..(club memberships are also a great way to get your name out...getting involved with your community will give you a boost also<your CoC can help with this one)
2)Tie in with other business..if Bobby's Mobile Bounce house is doing parties, try to find a way to get your Q there..this can be done by talking to Bobby himself and asking him to scratch your back...you'll have to do the same for him!
3) Find a mailing list and (you get the bulging envelopes like everyone else!) get your business in there with the others!
4) Invest in amazing biz cards (and pass them out), sponsor a t-ball team (or 2!), make friends with a journalist at your local paper and have them do a piece on your new endeavor,
5) Maybe get annoying with "take one boxes", door hangers, circulars, or flyers..
6) Radio ads are costly but effective..
Top-of-mind-awareness is crucial...do NOT give people the opportunity to forget about you for even 1 day---
I could literally give you over a 100 different things to do.. You have to be as creative as you can.
Things to Remember:
1) If you don't commit, your marketing efforts will be a bust.
2) Be patient..good marketing takes time..if you don't see instant results, that doesn't mean it's not working..people often need to see/hear something multiple times before they respond.
3) Be consistent in everything you do...DON'T keep changing things up!
4) It's INVEST not "spend"
5) Some of the tactics mention cost money and some don't..Don't just use one or two..If you REALLY want to get out there, try using 20 tools, or 40, or 60...seriously..and stick with them.. If your product is good and your marketing is solid, you'll have more trouble finding free time than you will finding the occasional 20 person work party..
The bottom line is this: people always say something will or won't help without every trying..people always shun something because it takes too much time and effort, people always avoid spend--which prevents them from "investing"...and all of these people fail..Do the exact opposite..no excuses..just do it..and you'll blow your own mind!
Hope this helps...feel free to PM if I can ever answer any more questions for you!