This is quite a good article from the Hotel Magazine: Social-Media Marketing for Restaurants: 10 Tips.
Even though this is meant for restaurants, I'm sure it applies to hotel marketing, too. The main point being that you actually think about how to use Twitter and Facebook before you start using them. Don't just create accounts because everyone else has one!
It should be pretty easy for you to determine your target audience. Choose the networks accordingly. Contrary to common believe, not everyone is on Twitter. In fact, it's only a geeky minority, although numbers are still increasing.
To find interesting topics and keep the news coming might be slightly harder. Tip number 2 from the article is essential - do some research before starting! Set up a research system for permanent use. The easiest and instant way of doing this is to use Google Alerts). Now you can react and respond if something is said about you. Responding to tweets for example is very important because Twitter and Facebook are conversational and not just one-way, even though that might be your first impression.
Respond to tweets in the way this blog describes it: Twitter's Real Value Is In Personal Connections.
Be visual! The number of tweets can be enormous if you follow more than a dozen tweeters. The most compellent tweets are those that have a link to click on. You are being led to a website with more information or even better something visual whether this is an image or short video. Images make your tweets personal, people love looking at them and they will also recall visual information much better when they come across another of your marketing messages elsewhere.
I also like point 5 in the article: create brand ambassadors. Let's be fair, there is quite a lot of work involved in keeping social media marketing afloat and it's taking up a lot of resources. Therefore, if you can find people who are passionate about your brand, utilize them. A good example are the Nike+ ambassadors who promote Nike events - and therefore the companies products - around the world.
Whatever you do with social media - and the possibilities are endless - do have a plan first!
You need to know what you are doing, put the necessary resources in place and last but not least measure the outcome of your social media campaigns.