When it comes to maxing out your mattress sessions, wetter is usually better. Since your natural wetness can decrease at times due to a variety of things (for instance, stress, medication and birth-control pills), adding lube helps ease penetration so sex is pleasurable and not painful. But using lubricant can be effective even when you don't have vaginal dryness. It boosts below-the-belt sensation and allows your man to thrust longer and harder without causing you discomfort.
Though lubrication can be made from water, oil, petroleum or silicone, water-based lube is your best bet: It's safe to use with condoms (oil- and petroleum-based lubes can cause latex to deteriorate); it's easily washed away (you're at greater risk of getting an infection with silicone-based lube because it isn't water-soluble, so it's more difficult to wash it and any lingering bacteria away); and it won't stain your sheets. If you're prone to yeast infections, use a water-based product made without glycerin (sugars found in glycerin feed yeast, causing it to multiply) for the same slippery satisfaction.
Once you've scored some slick stuff (try it out solo to find a brand you like), keep it close by your bed for easy access. When you and your man are fooling around, fire up foreplay by pouring a nickel-sized dollop into your palm and rubbing your hands together to warm it up. Then, slowly spread it over the tip of his penis and work your way down his shaft. Have him return the favor and smooth some over your hot spots, too. When you're ready to do the deed, give each other lube jobs again, only this time rub the lubricant over his condom. You can enhance his sensation by adding a drop into the tip of the condom before rolling it on.
During sex, replenish the lube whenever you feel a little dry. Simply stop for a second, have him pull out so you can reapply it over his condom, then let him glide back in. Just make sure you don't overdo it: A little wetness will ease penetration, but too much can make it impossible to generate frisky friction.