Best way to prevent water ingress at corner of lock-up/garage?

Hi, common problem, not easy to fix, i think first thing is to make sure that all clean and no rubbish if the garage has gutters make sure clean, and water running away to drain or soakaway, if know drainage the you could dig soakaway in that corner, nice deep hole filled with gravel, good clean at bottom of wall then sill with mastic, hope of some help colin.

Install a rubber type seal to floor base either directly under the door or behind the door similar to level access door to house. that way water cannot enter the garage. If you mean you have restricted access to corner of garage externally where wall is wet at ground level and rising then paint it with bitumen paint which will seal it to outside water coming in but you still need to find how the water is getting in and rectify that problem.