Identify your resume weaknesses and fix them. Or try reducing them. Some, like TPIC, are at the fate of seniority list progress. Others, like education, volunteering, union work, professional training, mentoring, working with the Flight Department, are not necessarily tied 1:1 to the seniority list.
Make yourself the best candidate you can.
The question has come up before - "I'm at a commuter as an FO. I can go to XYZ and become a larger jet FO or hope to upgrade at my current job in a year or two." The typical advice from guys, who aren't the decision makers but do talk with candidates and newhires, is typically 'take the upgrade'.
^^^ That becomes a tougher decision for the candidate who is 48 and not 28. The 28 yr old can wait. Or a 40 yr old with no college vs. the same 28 yr old. The guys less qualified vs. their peers have to consider "what if the majors don't call? What job will be a better long term option?" The 28 yr old has a long term outlook that the older guys don't have the luxury to have.
That's where the generic advice about taking the upgrade, even at lower pay, vs. taking a long term FO job that pay more might not be the best advice.