1. range of use.
Get is one of the most frequently used and most productive words in English. Often it has virtually no meaning in itself and draws its meaning almost entirely from its context, especially in idiomatic uses such as get to bed, get dressed, get home, get the flu, get a letter, get a new hat, get going, get rich, get one's feet wet, get a train, and so on. It will be seen from these examples as an all-purpose substitute for a whole range of verbs including arrive, become, buy, catch, collect, obtain, receive, etc. Get also has a highly productive role in forming idiomatic phrasal verbs such as get along, get at, get away, get away with, get back, get by, get down to, get on, get out, get over, get through, get together, etc.
2. supposed overuse.
The view that get is an overused word and should be avoided in good English is a superstition. It was not a problem for either Fowler (1926) or Gowers (1965), whose entries on this word dealt with different aspects of its use. There are some uses that should be recognized as informal, e.g. We got along fine might be better expressed as We were on good terms in more formal contexts and What are you getting at? as What are you suggesting [or implying]?, but there is no advantage in I received a letter this morning over I got a letter this morning nor in She's gone to collect her post over She's gone to get her post. Many idiomatic phrases involving get, such as get away with, get down to, and get to (= have an opportunity to:

• The problem with giving money to projects like these is that the general public never gets to see the results —Birmingham Post, 2000)

are effectively neutral in terms of register and can be used in virtually any context.
3. have got = possess.
This was one of the issues that Fowler and Gowers dealt with, as mentioned above. Fowler wrote that ‘have got for possess or have is good colloquial English but not good literary English’, and Gowers suggested that ‘the intrusion of got into a construction in which have alone is enough originated in our habit of eliding have. I have it and he has it are clear statements, but if we elide we must insert got to avoid the absurdity of I've it and the even greater absurdity of he's it.’ In negative contexts and questions, BrE have (or had) not got and have (or had) you got? is as common as (and somewhat less formal than) do (or did) not have, and do (or did) you have?, but the second alternative is the usual form in AmE.
4. The neologism get a life, meaning ‘to start living a fuller or more interesting existence’, is informal only:

• The aristocracy is having to make some hard decisions: whether to pretend that the twentieth century never happened or to jump ship, join the middle class and get a life —Tatler, 1993.

5. See also got, gotten.

Modern English usage. 2014.