I'm sure it depends on class, but I noticed a few bad habits I had when I first started DMing to improve.
Shooting people from behind in soap DM can be really bad for you and can translate poorly to in game mostly because how you practice is how you improve. You're basically shooting people who for whatever reason (music/no sound/care free) are not aware of your presence so when you switch to in game where people are going to be comming and usually pretty aware of where everyone is, you might find yourself struggling.
I wouldn't worry too much about if you're "back shooting" in DM, unless you catch yourself doing it quite often.
One for Soldier is mostly just constantly jumping, usually not landing for more than a second or two and then jumping again. You start to feel unkillable with regen and jumping to packs, this for the most part doesn't work in scrims or matches, as you'll be jumping people with buffs, not getting health back on kills and then promptly dying because you can't jump out with a full clip.