Freshman in college may be a bit early for a field school, but you WILL need one of these before you leave school if you plan to jump into the CRM game.  This early in the game, however, I would recommend any kind of volunteer work.  Passport in Time (http://www.passportintime.com/) is a good program.  The forums here tend to have volunteer opportunities.

If you are looking for paid field work experience, it may be a bit difficult with no "field school" to back you up.  Though it isn't impossible.  If you are looking in a specific region or country, you might want to post that since this board has numerous folks from all over the place who might know specifics.

In any event, good luck... this profession is not for the faint of heart. 

Reach out to your local/state historic preservation society and any historic preservation/archaeological institutions/groups in your area.

Contact your school's Anthropology/Social Sciences instructors.

I'd recommend signing up for a field school this summer.  I don't think it's too early; ideally you'd have a few courses in archaeology under your belt but I doubt you'd have any problem getting in.  If in doubt, contact the professor who runs it as early as possible.  This will put you in better shape for getting a paid position next summer or a funded research project before you graduate.  It'll open up a lot of doors.

Also, don't only limit yourself to your own school's field school.  There are a lot of them out there, find somewhere you want to work, somebody you want to work with, and a cost effective field school (I think most include housing & food).  There's a good chance the one running the field school will become your best contact when it comes to getting into grad school.

I took my first field school during my freshman year, infact I took a total of 4 field school courses. I also sought out any intern or voluntary position that would give me experience. One thing to consider is that experience is important in your future job opportunities.

You can check on this web site for volunteer and intern positions as well as on the National Park, National Forest Service, and state and local government web sites. Another good source is your professors. When you show a high interest in the field they can be very helpful. Professors are also a good source for finding volunteer and intern positions. 

Keep motivated and do not let negative responses or rejection stop you in your pursuit, just keep looking, that is what it is all about.  

Check out the passportintme.com web site.  they offer many types of experiences in archaeology and historic preservation through the US Forest Srvice and the BLM.

Field school is an absolute must at some point if you want to get into the field.  Volunteer work is helpful and fun, but at least one good field school is worth a whole lot more (note I said good field school - there are some that teach you very limited skills)  Also, keep in mind that even a good field school is limited in what it can teach you - based on location, site type, time period, etc.  so it is always helpful to get a variety of experiences in different settings.

Good Luck