Incense helps set the mood when I want to meditate or cast a spell. I light it as part of casting my circle, while facing east to welcome the sylphs of the air. There are scents to correspond to the days of the week or for certain goals, but if that gets too complicated, Nag Champa from World Market is a very nice everyday incense. (Their Champaka Flora is also wonderful.)
For greater variety they carry an economical assortment that includes patchouli, jasmine, lotus, pine, rose, sandalwood and amber.
There are excellent lists of correspondences in books and online, but here's a quickie for the days of the week. Then again, when practicing your craft use those other "i"s - intuition and inspiration - to select the scent that best suits you.
Monday - jasmine, sandalwood
Tuesday - Dragon's Blood (a personal favorite), patchouli
Wednesday - lavender, jasmine
Thursday - cinnamon, musk, sage
Friday - rose, sandalwood
Saturday - myrrh, patchouli
Sunday - frankincense, cedar, lemon
While sticks and cones are easiest to use, you can also use a burner and charcoal to burn resin or herbs. I recommend doing this outside as it can get smoky, but it does make a wonderful ritual for any sabbat or esbat.
Remember, too, scents can evoke memories. Shortly after beginning a regular routine of circle casting and/or meditating, the smell of burning incense alone may be enough to induce a trance-like state. Then try using the swirling, spiraling smoke for scrying. Blessed be!