Getting relevant experience before you apply to graduate school is really important. If your undergraduate major required you to do an internship of some kind, then you're lucky: your internship may be all the experience you need. But the more experience you can get, the better.
Of course, experience can be either paid or volunteer work--the graduate admissions committee members that look at your application won't care which you've done. Fortunately, most college students can find part-time work in jobs like the following ones: human service worker jobs in psychiatric hospitals, nurse aids in nursing homes, or jobs in prisons. These are the kinds of jobs that look really good on your resume and on your application to graduate school, because working in these kinds of jobs demonstrates to the admissions committee that you have experience working with people who have problems.
But if you've been having trouble finding a job in the social services field, you can always volunteer to get the same experience. Almost every nursing home accepts volunteers, for example. Keep your eyes open for volunteering experiences on your campus bulletin boards or in your local community. Contact your local United Way office and let them know what sort of volunteer experiences you would be interested in. United Way typically keeps long lists of local volunteer opportunities on file, and they can connect you with an opportunity that matches your interests.
Basically, admissions committees will be impressed if you can show them that you have experience working with people who are in trouble, and have the right attitude toward community problems. They will also want to see that you are a "people person", so even if you have only had past jobs in sales or customer service, it might be good for you to talk about these people-oriented jobs in your application essay.
In short, no matter where you live or what your circumstances are, you should be able to find opportunities to either work or volunteer as a "helper of people". Of course, this is especially important to do if you are just applying to get a masters degree (MSW), because the MSW is specifically designed to train you as a practitioner of some kind. However, if you already have your MSW and are you are applying for a doctorate (DSW or PhD), you will be better off focusing your energies on research experience. The D.S.W. and Ph.D. degrees are very research-focused, and it is very important for you to get research experience before you apply.
How can you get research experience? Get closer to your professors and find out if you can become a research assistant for them. If your social work professors are too busy to let you do research work for them, look in other schools and departments. The medical school at your university may be looking for assistants, and the sociology or psychology departments may also be looking for assistants. Also, it's possible that the place you work does research of some kind (e.g., many hospitals have research centers, and many other treatment centers do program evaluations), so talk to people where you work about what you can do to start out as an entry-level research assistant. Maybe all you will be able to do as a research assistant is administer simple surveys, conduct short interviews, or do data entry, but any research experience is better than none if you want a doctorate some day!