If you are writing for a journal that provides a document class or style package, use that.
If you are formatting it yourself, there are two options:
- the LaTeX article twocolumn option: \documentclass[twocolumn][article}
- the multicol package: \begin{multicols}{2}...\end{multicols}
The twocolumn option is built into the standard LaTeX article document class, but it fixes the format for all pages: there is no way to break out into single column (normal, wide) format.
The multicol package lets you change from two (or more) columns back to normal and back into two column whenever you want.
Caution: there will always be problems with figures and tables in two/more column formats: you have to read the journal's style requirements to find out about allowable placement, and whether they permit wide (full-width) figures.
///Peter