1. when used after a verb or an adjective, it means the beginning of an action or a state, and such action or state will continue, e.g. 大家都没来他就自己一个人吃起来了. He started eating even everyone else had not come yet. 他把我的外套挂起来。He hung up my coat. 小女孩一下子就高兴起来了。The little girl felt happy all at once. ***Besides, it also means "....when", or an estimate or evaluation sometimes, e.g. 这件事看起来简单，做起来很难。It looks simple, but it is hard to do it. 广州的夏天热起来可够人受的. The summer in Guangzhou is very hot. 看起来，今天不会再下雨了. It looks like it's not gonna rain today any more. 2. 想起来：to think of something, to recall, come to one's mind. e.g. 我想起来了，你是晓明. I remember, you are Xiaoming. 她想了半天也没想起来我是谁. She thought for quite a while but still couldn't remember who I am. 3. 起来 also can be used to indicate some changes, such as change from dark to bright, from static to dynamic, grow from small to big, from weak to strong, usually used with the weather , the color , sound , or volume, e.g., 天渐渐暗起来了。 It's getting dark. 她的脸开始红了起来。She began blushing. Hope it helpful. (*^__^*)

做起来这门生意-to excel in this business 起来！-get up！ 说起来，我还是挺佩服他的。-coming to think about it, I kind of admire him. the 3contexts that 起来would be used in:)

举几个例子： 1、快起来，不然就迟到了。（此处表达起床的意思） 2、起来，别坐在这。（表达站起来，向上、向高处的动作） 3、起来，不愿做奴隶的人们。（中国国歌第一句，表达拿起武器、发动攻击 ） 4、这个摩天轮转起来了。（表达某个动作开始了）

Usually when A says "起来" to B, B may sit or occupy a place, A would like to let B leave the seat or place, it's kind of like "Stand up" or "Move" in English, but it's a little bit impolite if you say so to strangers, close friends will be OK possibly. Hope this explanation can help.