Most regular gym goers have been off their normal training for the last 3 months. With fitness facilities opening nationwide (hopefully in MI in the next week or two) people are ready to jump back into their normal routines. However this can lead to excessive soreness, injury, and hinder gains/progress. Here are some basic tips on getting back into things.
1) Cut volume by 30-50%: If you were used to doing 4-5 sets of a given exercise drop it to 2-3 sets your first week or two back.
2) Keep effort levels at a 8 or less (on a scale of 1-10). Maxing out the first week back will put you at higher risk of injury since your muscles, tendons, and ligaments won't be used to the load. Plus the skill of the movement pattern won't be well practiced so you will be more likely to poorly perform the movement.
3) Take advantage of "newbie gains". Everyone who's ever started an exercise program can relate to the fact that the first 6-12 months of training are full of relatively effortless progress. Don't focus on what you used to do. Instead see where you are at, and enjoy the fact that you are seeing weekly improvements again.
4) Don't rush returning to previous volumes/frequency. The nature of adaptation to training is that over time you have to do more and more (sets, reps, weight, etc.) to continue to see progress. After 2+ months of detraining your body will be desensitized to training stimulus. If you are able to continue making progress with less frequent training days each week, or less total work per workout don't rush to returning to previous workloads. Instead relish the fact that you can now progress with seemingly less time and effort.