Shortly after I first started blogging about reading Chinese menus, I wrote an introduction to the concept of radicals. In brief, all but the very simplest Chinese characters are made up of a number of components, one of which is the radical. The radical is used to index the character in a dictionary, and also often gives some hint as to the meaning of the character (though this isn't always the case).
The radical I used as an example in that post was 魚 (yú/fish), which keeps the same form when used as a radical rather than a standalone character, though it will be "squashed" in some way to fit it in. When it appears on the left of the character, as in 鰻 (mán/eel), it's squashed left-to-right, whereas when it appears on the top or bottom of the character, as in 鱟 (wǔ/king crab), it's squashed top-to-bottom. A similar pattern appears in radicals such as 虫 (chóng/insect), for example in 蝦 (xiā/prawn) vs. 蟹 (xiè/crab).
However, some radicals change their form quite significantly from character to character, for example 水 (shuǐ/water), which often manifests as three slanted strokes (氵) on the left of the character. Another radical which appears in a few different forms is 心 (xīn/heart), which may also be seen as 忄 or as ⺗. Although few if any common menu characters have 心 as an actual radical, a number of them have it as what I'm calling a non-radical component. This is not, as far as I know, a recognised or official term, it's just a phrase that makes sense to me and describes an aspect of Chinese characters that I've found useful in remembering them.
By "non-radical component", I mean a portion of a character that is recognisably describable as a single unit, but that is not the radical. As an example, I'm going to deconstruct the abovementioned character for crab, 蟹 (xiè), which when I first met it seemed incredibly complex. Here it is in big:
As mentioned above, the radical of 蟹 is 虫, which here appears at the bottom of the character. Now looking at the rest of the character with the radical removed (some sources use the term "residue" for this), in the top left corner is 角 (jiǎo/horn-shaped), and in the top right corner is 刀 (dāo/knife) above 牛 (niú/cow). All three of these are characters I already know: 角 via 豆角 (dòu jiǎo/string bean), 刀 via 刀削麵 (dāo xiāo miàn/knife-cut noodles), and 牛 via 牛肉 (niú ròu/beef).
Hence, when I'm trying to remember how to write 蟹, I just need to remember to write 角 first, then 刀, then 牛, and finally put 虫 on the bottom. Some people like to make up little mnemonics to help remember these, though I find them more trouble than they're worth. (If you're a Skritter user, you can access other people's mnemonics and add your own while practising.)
This might all seem rather obvious, but when I first started noticing repeating components, it felt like a huge breakthrough in my understanding, so I thought it was worth mentioning!