There are many ways to better yourself at genealogy. One way is to volunteer your services to others. There are several ways for a genealogist to volunteer.
Genealogical or Historical Societies
Many (if not all) historical and genealogical societies need volunteers to help keep them going. Volunteer opportunities at these organizations may be helping visitors with their genealogical research, working in the administrative offices, cleaning, gardening, filing, etc.
Transcribe Data for Genealogy Trails
If you have access to non-copywritten genealogical records, and the time to transcribe them, you may want to consider hosting a state or county on Genealogy Trails. This site is dedicated to providing free records to genealogists, and they require a network of volunteers from all over the United States to help them. Not every area needs a host, so you will have to go to the site to determine if there is a need in your area.
Become a Lookup Volunteer
There are many places throughout the web where you can sign up to become a genealogy lookup volunteer. Two sites that are solely dedicated for free genealogy lookups are GenaLookups and Random Acts of Genealogical Kindness. As a volunteer, you specify which areas you are willing to provide free research in, as well as the types of lookups you can provide. While you cannot charge for your time looking up the genealogical information, you can charge for fees associated with the lookups (mileage, postage, photocopying, microfilm rental, etc.).
Transcribe Tombstones
This one is my personal favorite form of genealogy volunteerism, since I absolutely love walks through cemeteries. Sites like Find a Grave, Interment.net, and the USGenWeb Tombstone Transcription Project depend on volunteers to post photographs and transcriptions of tombstones. Some volunteers only post stones of their own family, while others spend time transcribing and photographing all tombstones in a particular cemetery (or many cemeteries) to add to these sites.