#1: Size of the vibrator.

This seems obvious, but sex toys come in many different sizes.  Your two main concerns are the girth of the vibrator and the length.  Smaller vibrators often have more concentrated power and can be easier to conceal (see Bet you can't tell it's a vibrator if that's a concern for you).  Larger vibrators can cover more area, but if you are a virgin or relatively sexually inexperienced, a large vibrator might be too much for you.

#2:  Whether or not the vibrator is waterproof.

Sex toys can be fun to use in the bath tub or shower, by yourself or with a partner, but only if they are waterproof.  If you think you might be using your vibrator in water, make sure you choose a vibe that's made for it.

#3: The purpose of the vibrator.

Some vibrators go inside the vagina, some are designed to go in the anus, some for any orifice, and others are not meant to be inserted at all.  You can usually tell by looking at it.  If it has a general penis shape, it's probably meant for the vagina.  If it has a wide base or it is extremely long and thin, it's probably for the anus.  Vibrators that are meant for clitoral stimulation come in a variety of shapes.  Of course, anything that vibrates can go against the clitoris.  Check out the feature on each item's page that says "For body part" if you're not sure.

#4:  Special features of the vibrator.

Vibes often have special features that you might like.  Many have nubs or other textures.  They often have variable speeds.  Some are electric (and therefore claim to be more powerful).  Some are controlled by a wireless remote.  Some vibes have extensions at the base to stimulate the clitoris while the larger part is inserted in the vagina.  Some strap on.  Some are meant to look like a penis.  Some are colorful.  Some are scented.  Some are designed by famous porn stars.  Some you can attach to your tongue to give your partner a special thrill.  Some go right in a pair of panties.  Etc, etc, etc.  Basically, there are tons of differences between each type of vibrator, and if you figure out what excites you, you can find one that's perfect for your pleasure.

#5: Price of the vibrator.

Vibrators can range from under $10 to over $100 or more.  If you've never bought a vibrator before, I would recommend sticking with a toy that costs less than about $30 (don't forget lube!)  Then, after you find out what you like, you can buy additional inexpensive vibes or opt for a higher-end toy.  If you find a toy that looks like a lot of fun but costs more than your budget can afford, you can often find one that's very similar for a lot less, if you take the time to look around a bit. 

Good luck!

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