Mike was hired to assassinate Tuco Salamanca by Nacho in fear that soon Tuco will fly off the rails and kill Nacho, but Mike changed the plan to get Tuco thrown in jail instead, by getting him to steal from, and fight Mike, while police came. This worked, but Hector Salamanca, Tucos uncle (bell wheelchair guy from Breaking Bad), came to Mike and told him to confess that the gun found at the scene was his, so that Tuco would get off, Mike refused. So later the Cousins from Breaking bad, also nephews of Hector, show up to threaten Mike. He then goes to a sit down with Hector, who threatens his granddaughter, but agrees to Mikes terms. Mike recants his statement that the gun wasn't Tucos, with Jimmys help. Charges are not pressed on Mike, and are dropped or lowered on Tuco. Mike retaliates by disrupting a money transport, but is dismayed to find out that it did nothing except get an innocent killed. Mike decides to kill Hector, either to protect his granddaughter, or to get revenge for the person that died, or anger. It's not really specified from what I remember. Nacho keeps blocking the shot. The driver that he didn't kill in the money transport is murdered. He hears the horn, goes back and finds the 'Don't' note. Begin Season 3.
That's about everything that happened to Mike last season, that's relevant to this season. I doubt the squat cobblers will matter much.