To contact any being, elemental angelic or otherwise, you don't always need a ritual unless that being won't be summoned by any other means - some beings require that you go through certain formalities to contact and work with them and some don't. All you need to do is concentrate on the name of the entity in question, and 'will' yourself to make mental contact with them. Repeat the name as a mantra with the intention of catching that entity's attention astrally/mentally. If you believe you can, then you WILL...eventually, anyway. I usually relax and clear my mind through meditation, then concentrate on activating chakras and pranic tube, and then I try to contact an entity while using his/her/its name as a target. Pictures can be used as targets too (which is why I NEVER put my picture online for others to see - I don't wish to be incessantly poked mentally or astrally by uninvited people unconsciously or otherwise. It's annoying!).
Sometimes it helps to imagine that you are in the presence of the entity or person you wish to contact. If you know the person/being personally, then you can imagine how it feels to be in his/her presence, how they look, the smells you associate with him/her, etc. All these things help you to tune in to his/her astral frequencies and make your efforts for contact more successful. You can do this with a human or a spirit.
Humans don't always know consciously when you're contacting them, so often you'll just get an aspect of their consciousness that they're not aware of or they'll just start thinking about you and dismiss it as coincidence that they thought about you. In the case of skilled magickians, often they'll know someone is trying to contact them and either turn around astrally in their minds to speak with you or they'll tune you out if they don't have time to speak. Most just find it annoying to be bothered constantly and will ignore anyone not within their immediate circle of human contacts.
If you think about someone intensely and suddenly you get the feeling that the mental image of that person in your mind has more 'life' and autonomy that it should, then it's possible you've contacted an aspect of that person without realizing it. That's how some magickians learn to contact spirits, by the way. They imagine an image of the spirit according to traditional rules, and then they practice interacting with that mental image and putting words in that image's mouth and making it move around etc. Until one day the image takes on a life of its own and starts moving and speaking on its own! That's apparently how Lon Milo Duquette learned to speak to spirits - entirely by accident.
Using this technique with living people can sometimes result in actually contacting that person's spiritual aspects by accident - especially if you include lots of additional mental aids like visualization and remembering smells and the feeling of that person's presence etc. It can really piss-off people who are psychically inclined when you accidentally contact them by imagining their presence so vividly, so be careful. Don't use these techniques for childish games. Be grown-up about it.