Read the articles Gail mentioned.

As noted, you need log backups. The transaction log will keep all data around on transactions until it is backed up (some exceptions for mirroring or replication), so you need log backups.

If you aren't sure how often to run log backups, ask someone how much data you can lose in a disaster. They will say none, but that costs $$$. many orgs can survive an hour or two of data loss, but whatever the number, that's the frequency of your log backups.

We have a great script here [/url]to help with this that is better than maintenance plans, but you can use a maintenance plan if you like. Make sure you are only doing the log backups for those databases with full recovery model.