
First of all - the
size. The dills vary widely in length and width of penetrating shaft.
Some people like their dildo to be big just enough to feel its presence and motion. Others enjoy the sensation of being stretched and filled. For most people the width of the toy is most important factor in their sizing preferences.

When deciding on how
wide or slender your toy should be you may want to experiment with different positions and movements. When ready to order, please, keep in mind, that the toy's width is usually expressed as a diameter which measures it across the shaft not in perimeter.
If you enjoy the deep penetration the length of your dill is just as important. 7-1/2" or longer dildo might be a right choice for you. After all, you always can thrust a bit less than a full length, but it will be impossible to reach further with a short dildo.
Deciding on a dill's
length, consider that you most likely do not want the toy reach and bang against your cervix. For most women this stimulation is less than pleasant. If you are one of these women, make sure that the insertable length of your toy is no longer than you can stand it. The insertable length is the one which measures from the tip of a toy to a bend or flange beyond which the dildo cannot enter you vagina.

If you plan to use your
dildo in harness, keep in mind that the effective insertable length of your dildo will be reduced by 1/2" or so. However, do appreciate that unlike holding a dildo in your hand you will have much less control over the depth of thrusting. Make sure that the dildo is not too long to touch the cervix.

If you are choosing a dildo for
anal stimulation, don't forget that the straight section of rectum is 3" to 5" long and, unlike vagina, it does not expand with arousal. You might want to limit you anal dills to this length or chose the ones the bend around this length. If you still prefer a longer toy, it should be soft and flexible enough to bend itself to your natural body shapes.

The toy's
shape, style and color are very much a matter of your personal emotional preference.
Some people like their dildo the better the more it resembles a real erect penis. Yet others prefer to play with the very abstract dills. For those undecided there is a great range of options in between these two alternatives.

And finally, the
material your love toy should be made off.
The right decision on this feature will come from a balance between your personal tactile sensorial preferences and your concerns and practices in issues of health and safety
We have a whole chapter that discusses the sex toys materials.
If you ready to read it now, here is the direct link to
it:
about materials.