This video is one of the better introductions to various bypasses. Even if you don't want to watch the whole video, I recommend watching from 3:30 - 9:00 and from 11:20 - 15:20. The majority of buildings have at least one door you could get through with these tactics. A tip on latch slipping: if the deadlatch is engaged, but the door opens outward, you can often lean on the door and push in on the deadlatch to get it to disengage. And you don't need a special tool, I've done it with paperclips and bent nails.