How is clinical research different in what I will be doing compared to basic science research?
That's a very broad question, it depends on what kind of basic science research you did and what sort of clinical research you are going to do.
In general, clinical research is harder since you usually get one shot to get it right, you don't get mulligans.
For example, if you are working with mice tissue samples and screw them up somehow (mix them up, perform wrong extraction, improper storage, etc), it can be a big problem but you can always redo the experiment so it isn't necessarily a show stopper. But it's pretty much impossible to ask a patient to undergo another biopsy. Or when you are doing a retrospective study there's really no way to reconfirm an observation other than what was written down.
The other issue is the paperwork; you have to keep track of consents, deal with issues of confidentiality/deidentification, IRB audits and reports (there are a lot of things like deviations and adverse events that have to be reported within a specific timeframe).
It just depends on what sort of clinical research you are doing (ie retrospective, observational, clinical trials, etc) and your exact role.
I can tell you the my biggest pet peeve is people being sloppy. I'm not saying it's intentional or even laziness (I don't go to the clinics often but I know enough to know that it can get very hectic at times), but things like mishandling samples by not storing them properly (freeze/thaw artifacts evident in tissue samples) or entering physiologically improbable numbers just annoy me. I think at least part of it has to do with the nature of clinical research, there's just so many people involved and most of them are so far removed for the experimental design and analysis that they don't feel ownership over the project, but that's a different discussion.