Before the show, practice together as a band and practice hard. This might sound a like a no-brainer, but consider that the CD release party is a big deal for your band and it is likely to be the first time some potential fans hear your music. Additionally, because you are releasing new music, it may be the first time you've performed these songs live. Make your first impression with the crowd count, and have these songs down cold.
Tell people to show up. Otherwise, you'll be playing for crickets and the bar staff. Social media has accelerated the way bands deliver messages, and you should definitely send out online invites. Don't neglect more traditional methods, though. Go to shows of bands that have similar qualities and pass out invites. Similarly, blanket the town with show fliers that are clear about the location, cover charge and any special events you've got planned for the evening.
About three weeks prior to your CD release show, it's a good idea to hand a copy of the recording to local media. Write a press release detailing the release date and venue information and distribute copies of the release and album to traditional mediums such as newspapers and local radio stations. Also, locate any local music blogs with large followings and give them a copy, too. Anytime one of these outlets picks up a story or relays the information, it increases the chances of having a large crowd.
Your fans likely see a lot of concerts, so make this one different from others. Hand out T-shirts or copies of your CD between songs. You can also create a theme using elements from the CD or its artwork, and you may want to decorate prior to the show if the venue will allow it. Also, donating some or all of your proceeds to charity is a good gesture. Remember, more so than other gigs, you're using the CD party to build a fanbase. Donate money the first time around, and fans might come back with friends you can profit from at subsequent shows.