Read the "Avoiding Square Corners" Thread in the Hiring Topic. Not step 1, more like intro to the entire topic. Then...

1. Read the airline profiles on top of the web page.
2. Get ATP and Class 1 Physical Done.
3. Draft your Flying Resume.
4. Start Building Profiles on airlineapps.com and pilotcredentials.com.
5. Call everybody you know who is an airline pilot, wannabe airline pilot, every reserve squadron you know, and start asking questions.

That is a lot. Good luck getting started.