There is a specific section on VMCAS (the universal program/form thing we use to apply to all vet schools) that asks for veterinary experience. Many applicants have hundreds or thousands of hours working or volunteering for a veterinarian. The greater the variety of experiences you have, the better it will look.
There is also a section for animal experiences, which are experiences that involve animals but are not under the direct supervision of a veterinarian. This would be, say, volunteering at a local humane society or rescue.
This is just a vague idea of what sort of things the admissions committees are looking for. Of course, different applicants will have different stats, and there's no universal formula for being a "good applicant," but having experience hours is necessary.
Also, as DVMOB mentioned above, you need at least one (and for some schools two or more) letter(s) of recommendation from a veterinarian. This vet can not be a family member, and must be able to comment on your ethics, work ability, professionalism, personality, etc. etc. so they actually have to know you.
I'm trying not to sound harsh or bossy - just informative! I'm sure you are an excellent applicant otherwise, but the experience thing is a requirement. So, if you would like to apply this fall, you will need to start working on that right away. Good luck, and feel free to ask if you have any questions!