Do a good deal of research on conjuring and work on spirit communication before attempting evocation or invocation.
It is advanced work because it eventually becomes a working relationship with various spirits. Really once you cross that boundary you don't want to go back.
Try a trusted intelligent force such as is seen with the Norse runes first. Although the runes are by no means easy or weak, channeling energy of such "spirits" is consistent and controlled, so you know what you are getting yourself into. When you evoke for the first few times I recommend having a strong spiritual guide/guardian, physical mentor, or experienced practitioner present in case anything goes wrong. If it feels right to you to begin a relationship with a deity, you can invoke them to evict a unwanted presence that is trying to dominate you. Otherwise, a rune like Algiz or even Thurisaz invoked can be used to do so. Always have a plan A and plan B of "what if" something goes wrong.
Once you have a good trustworthy relationship going with a spirit, the hardest part is over. It's always most difficult when first starting out.