Here are a few that I've seen happen time and time again in psychology labs - the main solutions are related to paying specific attention to data management issues that are not typically part of research psychology instruction (but should be).

Failing to keep redundant copies of original data. Even if automatic backup procedures are in place, it is important to make sure they are doing what you think they are doing.

Failing to document original data so that someone else can understand it. I don't know how many files I've come across with experimental conditions labelled "A,B,C" or similar, that can no longer be reconstructed. Including data generated by my past self, I'm sorry to say.

Failing to retain a clear and replicable sequence from original data to "results". If an error creeps in, much harder to figure out where it came from.