As a general rule, one should never sign any legal document before consulting with an attorney.

Subrogation allows your insurer to stand in your place and seek compensation from the party at fault. The idea is that they should be made whole while at the same time the injured party (you) should not be able to collect a windfall by being paid twice (once via healthcare once via damages in a lawsuit). Subrogation rules differ by state and can adversely affect your compensation should you decide to sue.

It is important that you seek legal counsel before signing away your rights in any subrogation agreement.

Most importantly, don't take you buddy's advice. No two lawsuits or circumstances are alike.