@Nhi Nguyen, with AB 1482 there are quite a few restrictions on getting tenants to leave without due cause. Alameda County also has its own set of issues, as I am sure you are aware. My approach in this area has been:
1. Make sure that your tenants are not violating the tenancy occupation rules. Typically, you may find apartments with more people living there than the lease. Provide them with a 3 day cure or quit notice immediately
2. Make sure there are no trouble makers - with other tenants, noise, etc which violate your posted rules. Provide them with a warning and if they don't satisfy it, then the appropriate number of days notice - either 60 days or 90 days (I think)
3. Make sure that your tenants pay on time and if they are late by a day, then provide them with a 3 day cure or quit notice.
The goal is not to remove tenants that are following the rule, but those that are not. In a well managed 12-15 unit property, this will give you at most 3 units that can be turned. Any such vacancy will allow you to remodel and reposition for higher rents. It is possible that your existing tenants may want to move into such a unit, and given that MTM position and your appropriate rent increase given in the last 12 months, you may be able to increase their rent by the allowable maximum, giving you another unit that you can remodel and continue the process.
Since you seem to have the right background, do make sure that no large deferred maintenance issues exist since that becomes another source of contention with providing proper housing to your tenants. Good luck.