Always start with a clean and moisturized face so that your makeup application works and looks its best. Moisturizer can also help diminish the look of fine lines, but don't apply too much; super-lubed skin can make the makeup slide south.
Use a makeup putty if your lines are bugging you. Putty fills in fine wrinkles to give the appearance of smoother skin. You can find it at any cosmetics counter. The key is to use a small amount and slowly build up the product in the fold. Blend the surface with a makeup sponge.
Apply your base foundation as usual, then blend well. Add a very light dusting of face powder to set the base, if necessary, but don't use too much -- powder can create more issues, such as aging instead of flattering.
Use a small pointed brush to apply a concealer or highlighter to the laugh lines. Placing a highlight in the fold will reflect the light and reduce the intensity of the fold. The key to applying concealer is to build up layers until you have the coverage you want. Blend well with your makeup sponge.
After you've done your best to hide your laugh lines, go ahead and bust up all you want. Laughter is good for the soul. Whatever effects laughing may have on your face are well worth the price of a good chuckle, no?