Today is the big day.

The caucuses, which will take place on tomorrow, is the kickoff to the primary election season to help determine who the Republican and Democratic presidential nominees will be. There are currently 12 Republicans vying for the Republican presidential nomination and three candidates vying for Democratic nomination.

RELATED: Iowa’s changing caucus landscape

Whether it is your first time or your 50th time caucusing, here is how to get ready for the big day.

There is only one way to caucus in Iowa, and you must be a registered voter.

Registration can be done at your precinct caucus site, which can be found in respective party website. (Democrats, here. Republicans can find their precinct here and their caucus locations here.

Those who are registering the day of should get there earlier than 7 p.m. Caucuses will begin at 7 p.m. Voters must be registered with the party they are caucusing for.

Here’s how to register to vote in Iowa to caucus in Johnson County.

• Go to your precinct caucus site

— Bring your driver’s license or state ID

— Bring your Social Security card or know the last four digits of your Social Security number

— Bring a piece of mail, such as a bill, to confirm your address

— Sign which party you are registering for

— Caucus

— NOTE: The Democratic Caucus does not require an ID or something to confirm your address.

How to caucus for each party:

Democratic Caucus Process

 — Be at your precinct caucus site at 7 p.m.

 — Sign in/register

 — Split up into preference groups

Do you have at least 15 percent of the attendees present at the caucus in your group?

Yes

— Then you are a viable group

No

— Then your group will either have to try to recruit attendees that will support your candidate or you will move to a “viable candidate”

Precinct captains will then use a calculation to determine “delegate equivalents” for each candidate

Republican Caucus Process

— Sign in/register.

— Jot down your preferred candidate on a sheet of paper.

— Bring the paper to the designated official.

— Precinct officials announce results in front of the whole caucus

— The precinct results will be reported to top party officials.

— The Republican Party of Iowa adds up all counts across the state to decide a winner.