Every month there are sign up incentives and with the holidays rolling up this is a good time.
Best tip is to sign up with one company the first moth, meet the driving requirements to get your bonus. After you have done your minimum rides and you have been notified that you have a bonus coming, simply sign up for the second company and drive to get that sign in bonus.
Drive for Uber:
https://partners.uber.com/i/rouhg
Drive for Lyft:
https://www.lyft.com/drive-with-lyft?ref=TONY083870&utm_medium=d2d_referral_email