My husband and I try to sneak a "date night" in at least once a month, and we are lucky enough to have two great babysitting options - our daycare provider's 14 year old son and 12 year old daughter. The situation works perfectly for everyone - my kids (ages 3 and 7) have been a part of this daycare family for 5 years, the sitters live close by, and usually their mother is home as a backup in case of emergencies. Some parents may feel that 12 or 13 is too young for a sitter, but not if you weigh the other variables (experience, maturity level, comfort level with children). If you are unsure of the proper age for a babysitter, consider the pros and cons of the following age ranges:
Pre-Teen Sitter - Many babysitting courses require their students to be at least 11 years old, and I wouldn't consider a sitter younger than that. I would be uncomfortable leaving a 10 year old at home by him or herself, even without being in charge of younger children. If you are considering an 11 or 12 year old as a sitter, girls are usually more mature at this age than boys. I wouldn't leave an infant in the care of an 11 year old unless he or she has a lot of experience with babies (younger siblings or cousins). I would also hesitate to hire a pre-teen sitter for an older child (9 or 10) because of the small age difference. The child may see his or her sitter as more of a playmate instead of a responsible caregiver. I also do not recommend leaving pre-teen sitters with your child(ren) for more than 8 hours or overnight. When we hire a younger sitter we either feed the kids before we leave or we have an easy meal planned (one that doesn't require the use of a stove).
13 to 15 Year Old Babysitter - This may be the perfect age range for babysitters - they cannot drive yet, are not immersed in social activities, and are usually not old enough for a "real" job. I have found that my boys love to play with Josh (our 14 year old babysitter) because he likes more masculine games like Smash-Em-Up-Trucks and football. Josh also loves the extra cash and is great with kids - probably because his mom has done daycare his entire life. Even with Josh's experience, I'm not sure I would be comfortable leaving him with an infant that requires high maintenance, and I still don't ask him to cook meals on the stove.
16 to 18 Year Olds - Although this is a great age for sitters, I've had a lot of trouble finding an older teenager who is interested or available to watch my children! They either already have a job, have "plans" for the evening or they are just too cool to babysit. My close friends do have a 17-year old girl who watches their infant, and it's great for them because not only does the sitter drive herself to and from their house, they feel comfortable leaving their 9 month old with her for long nights out. The downside to this is that my friends pay more for this sitter to watch one child than I pay my sitters to watch 2 kids, but it's a trade-off that they are comfortable with. I would feel at ease allowing an older teen to use the stove, watch numerous kids at once, even stay overnight if necessary. I would also allow an older sitter to take my kids to the park or on a play date with other children.
College Age Sitters - I'm not lucky enough to live in a college town, but if you are then this may be a great resource for you! Every college student I know needs more money, and they can use their down time (after the kids have gone to bed) for studying. The older your sitter is, the more responsibility you can give them (driving, cooking, etc), but you will also have to pay them more. If you have a regularly scheduled night where you need a sitter (i.e. bowling night or "girls night out"), this arrangement may work very well because a college-age sitter can pick up the kids from school, help them with their homework, bathe them and put them to bed while you enjoy your time away.
Adult Babysitters - If you are lucky enough to find another mother to trade babysitting duties with, this is a win-win situation for all! Rather than paying for a sitter you may be able to swap services (just make sure there's a fair trade). If you can't swap sitting you still may be able to find an adult who has time to watch your children, but they may want you to bring the kids to them and they may charge more than a younger sitter. I'm not lucky enough to live near my parents or in-laws, but many grandparents are providing daycare or babysitting services for their grandchildren - this helps them spend quality time with their grandkids and it gives them something to look forward to if they are retired. In some situations, parents will not pay for the babysitting but they may perform household chores or buy grandparent gifts.