I don't really recommend memorizing kanji readings. In fact, I would advise against it, because rules for kanji readings aren't consistent enough to be of any use.
Kanji readings are categorized as Chinese reading (onyomi) or native Japanese reading (kunyomi). There's a general rule stating that kanji compounds (words that are composed of two or more kanji characters) use Chinese readings, and words with single kanji characters use native readings. For example, 先生 (teacher) reads せんせい and 力 (power) reads ちから.
However, many kanji have many Chinese or native readings. For example, 人 has にん and じん as its Chinese readings, while 生 has せい and しょう. So, how are we supposed to read 人生 (human life)? Is it にんせい, にんしょう, じんせい, or じんしょう? In the end, beginners still have to use their dictionaries to find out that the correct reading is じんせい.
And let's not forget that Japanese language is littered with exceptions. For example, according to the rules, kanji compounds use Chinese reading, so beginners would think 名前 (name) must use the Chinese reading めいぜん, but the correct answer is actually なまえ, and that's the native reading kunyomi.
Not to mention that there are some words which ignore kanji readings altogether. It's just impossible for beginners to know that 明日 (tomorrow) reads あした or that 大人 (adult) reads おとな with only the knowledge of these kanji's readings. The kanji are there only for the meanings. おとな is known as 大人 as a whole. You can't break おとな down and assign each kana to 大 or 人; it is the reading of the whole word, the combination of these characters. And, again, beginners have no choice but to consult their dictionaries.
My advice is, kanji readings are easier to remember in real usable words, not individual characters. Think of something that can be used in real contexts.
For a word composed of a stand-alone kanji, remember the correct reading of the word.
Remember 力 (power) as ちから, not りき or りょく.
Remember 人 (man) as ひと, not にん or じん.
For kanji compounds, remember the reading of the whole word first, then break it down if possible.
Remember 大学 (university) as だいがく, and you'll also get that 大 = だい and 学 = がく.
If you remember individual kanji first, you'll know that 大 = だい/たい and 学 = がく, but you won't know if 大学 is だいがく or たいがく.