Sometimes the most simplistic method can be the most effective for a given individual.
The simplest method for memorization is to read and reread the item being memorized. Cover the item, and repeat it to yourself. If the item is long, learn it in sections, and keep repeating each section as you add the next section.
Eventually, have someone else quiz you on what you are memorizing.
Many people find memory tricks helpful for memorization.
A popular memory trick for remembering something like the order of the planets is to create a sentence using the first letter of each planet as the first letter for each word on the sentence.
If order does not matter when memorizing a list, it is sometimes possible to take the first letter of each word and arrange the group of first letters into a single word.
It is also possible to create memory tricks of your own by remembering the key is making the information more concise, and thus seemingly less to remember. For example, if memorizing a poem, remember the key meaning of each stanza. Then, attempt to memorize the individual lines.
Some information is not possible to reduce to lists or single words, but must be remembered in large chunks. For example, memorizing a speech, long quotations or historical facts requires some inventiveness.
It is best to memorize this sort of information through understanding. Become as familiar as possible with the nature of the information, and find triggers such as associations to better remember what leads from what. If you are attempting to memorize the age order of the children of Catherine De Medici, think of a family already familiar to you from history, television or personal acquaintance, and think of the children as each of the children in the already familiar family.
A method which works for some is to put the information to music. The rhythm of an already known tune can assist.
Alternatively, word association to already familiar terms can be simpler and equally as effective.