I agree, being in an area already populated by a number of restaurants can is a good thing. It means more traffic. There's a reason you see restaurants grouped together and why many corporations often open up different concepts right beside each other (think Red Lobster and Olive Garden which both were owned by Darden).
As much as some people here are going to hate me for saying this-you really need to embrace social media to get your message out and help to build your following.
Beyond that, make sure that you are offering something the other places aren't and work with your staff, constantly, to ensure both the service and the food is top notch, for your concept. Give people a reason to come back. Offer incentives such as loyalty cards, if your place is that kind of restaurant (meaning I wouldn't do it if I was fine dining, but most definitely if you are a sandwich or pizza place).
Get some press releases out there. Make sure the local paper knows you are there so you can get reviewed, or if you are in a smaller community like me, the opening of a new place can be newsworthy itself, especially if you are local and going up against national chains.
In the past I've also gone out and given menus to hotels and have even gone so far as to give front desk staff and managers coupons for free drinks or free meals to get them excited about the place. That excitement will yield recommendations.
Of course, you can always spend a lot of money on a marketing campaign, but if you are a small, independent start up, that isn't always feasible. You just need to come up with creative ways to market yourself.
If you give us a little more information about what kind of place it is, we might be able to better help you out with ways to market your place that won't break the bank.