OK, so you have a new client and a new assignment now. What do you do?
Well the "knee jerk" response is usually... do a great job!
WRONG. That's not enough.
You want your client to come back to you and only you. To do that you should also be educating your client about all the "extras" you are handling to make their project really fly.
Now as a designer you might be doing things all the time that are second nature to you. BUT for other designers not as experienced, if they miss these things there could be production problems.
For example... all the photos your client sent. You checked them to see if they were high res or low res, you checked to see if they were RGB or CMYK and then made the correct mode change for the medium they were sent for. You might have removed clipping paths. That Illustrator file... you got rid of hidden layers that could print. How about all those Photoshop files where you discard color profiles that could screw things up.
How about talking to the printer. When you did an animated banner.. all the work involved to make sure the banners didn't exceed the max sizes demanded by Google or other companies.
Bottom line... doing a great design job is important.. but just as important is educating your client to all the extra benefits there are when they work with you. That you are giving them more than just a great design, you are giving them files that will the printers will love. That they won't be spending more money getting corrections done at the printer. Or that your web files will work across all browsers. When your clients trust you, you will get more business.