How to resolve UNABLE TO LOCK ROW error in salesforce?

Reason and Resolution- 

When you have multiple jobs running that update the same set of records, it's recommended to lock the records using the FOR UPDATE keyword. It will ensure that the record is locked and no other job can update the same record at that point in time. The conflicting job will then wait until the locking on the record is released and then perform the required operations. This will avoid conflicts between jobs that are running concurrently and will not throw up this exception.

Locking Statements-

In Apex, you can use FOR UPDATE to lock sObject records while they’re being updated in order to prevent race conditions and other thread safety problems.No other client or user is allowed to make updates either through code or the Salesforce user interface if the record is locked.

Ex. Account [] accts = [SELECT Id FROM Account LIMIT 2 FOR UPDATE];