1. Find a space that can serve as an Altar. A table or a cleared space on a counter-top would work nicely. You can make the space as simple or as elaborate as you like. Knowing what colors are sacred to the spirit, you may choose to cover the space with a cloth of those colors. Collect items sacred to the Loa you wish to work with. Often, you will be working with more than one Loa, unless you are only working with Legba. This is because Legba is petitioned before calling upon any of the other Loa, since he is the Gate-Keeper. You can find this information out by looking for the name of the Loa you wish to work with here and selecting his or her name. This will open their page, which contains their correspondences, songs, offerings, etc.
2. Cleanse your space. For this, I perform the Lesser Banishing Ritual of the Pentagram. However, you may choose to take a Cleansing Bath and smudge the area with Incense like Sage or Frankincense and Myrrh, instead. Either method is fine. The point is to cleanse yourself and your space of all energies accept those you are working with (the Loa).
3. Energize yourself and your space. For this, I perform the
Lesser Invoking Ritual of the Pentagram, Lesser Invoking Ritual of the Hexagram, and
Ritual of the Middle Pillar. These rituals charge your area and yourself with Divine Power, preparing both for work with the Loa.
4. Lay out the Loa's Veve (if you've not already done so in step 1) and the offerings you have for him or her.
5. Light a candle of a color appropriate to the Loa, invoking him or her by singing or chanting their song, or chanting their name, etc. Ask the Loa for what you seek. This can be done with a simple prayer, a thorough conversation, or something between the two, asking for their assistance to help you obtain what you seek.
6. OPTIONAL: You may decide to make an agreement, such as feeding him or her
(giving the Loa another offering) once you've acquired what you've asked for, etc. Should you decide to do this, make sure to fulfill your promise, as breaking your word to the Loa, or any other spirit, can have disastrous consequences, not the least of which might be the loss of what the spirit helped you get.
7. Leave the altar, offerings, etc. in place until the candle burns out. Then, dispose of your offerings in a sacred manner. This can involve burying them in a place sacred to the Loa or spirit you are serving\working with, or simply putting the offerings into a small trash bag, tying that up and placing it into your normal trash. The extra bag is to keep it separate, etc. and is a modern variation that I, and many others, have used with good results.