How are the Republican and Democratic nominees picked?

Question

Does a committee pick, is it a vote by all party members, or something else? Also, when will the nominees normally be picked?

I think I got the terminology wrong. I meant how is the candidate for the general election picked.

Answer 1

THe candidate must register to run in each of the 50 states, be a member of the party and pay a filling fee in each state

Answer 2

Obviously you are not from the U.S. because such things are learned in school starting about the fifth or sixth grade. So even though I really would like to answer "they pick a name from a hat", here's what really happens:
Political parties hold national conventions with delegates from each of the states mostly based on population numbers. What that means is a state like NY would have a large number of delegates while a state like Montana would have fewer because more people live in NY than in Montana. The individual states will have previously held their state conventions and will have elected delegates. These state delegates may have been "pledged" to a particular candidate and that's who they would vote for at the national convention. A candidate must receive a majority of the votes at the delegates meeting in order to be that party's nominee. Sometimes that doesn't happen on the first vote or second vote. Sometimes they take LOTS of votes until a consensus is reached.

Answer 3

They are picked by whoever does the best during the primary process and can get the most delegates from the states to vote.

If a candidate wins a state's primary election, he wins the votes of the delegates from that state at the National Convention.

Answer 4

whoever feels like getting out of bed votes in the primaries, and you have to sign a statement saying that you belong to that party and will only vote in that party's primary.