You can implement the following strategies to successfully use Twitter:
Retweeting a statement by a company or individual is almost like telling them: follow me back. And most will do. Make sure the tweet is relevant to your business.
Reward a customer... out of the blue.
Choose one of your followers and give him a free drink, lunch or dinner. Not only will they be surprised and happy but they will be sharing it all over social media.
Customize your account
Make sure you look professional on twitter. You can customize your background, have a professional profile image and put your brand in the spotlight. Don't forget that people often discover your restaurant on twitter for the first time. So you want to make a hell of a first impression.
A quote a day...
Why don't you post inspiring quotes, one a day. Post something fun, inspiring or both. People not looking for restaurants may stumble upon it and retweet it anyway.
The making of
I guess not all of your customers have been in the kitchen or back of house. Wouldn't it be fun to post from time to time a behind the scenes photo? It's also a good time to post a photo of staff having fun at the job. An impression of good team spirit will lift the corporate image of your establishment.
Twitter is a great way to get an opinion from your followers. You can post a survey or a poll to get a feeling of what you should buy: that terrace heater or a kids corner... ;)