Here are some tips I outline in my blog post on http://momprojects.com
1.) wood selection- I used pine. I think I would have used poplar if I did this all over again. I found out it is a bad idea to put pine through a joiner and planer due to the sap gumming up the machine. Therefore I was not able to properly mill the boards before starting. It didn't cause the bench to be misaligned but may have been slightly easier to put together had I squared up the boards. Sorry pine...I love you but can't have a sticky joiner!
2.) I built this quite a bit longer than the plans called for and so, for support, I cut 3 boards and kreg jigged them together in the shape of an 'H'. the top and bottom were cut to fit the width of the inside of the bench and the middle board that connects them I cut in the height of the bench (minus the height of the top and bottom support board). Set the 'H' in the center of the bench and use your kreg jig to attach it (mine is way off center but still works great)
3.) It is worth the investment to throw some molding around the bottom. I saved money by not putting molding on the back. I also used a lower grade pine for the sides and the back. In retrospect I probably should have done that on the top too since there is going to be a cushion on it. Oh yea..I am making one and will post it as soon as I do!
4.) Attach the hinges and put the entire top together before attaching it to the bottom part. For some reason getting the hinges on was a little tricky and I suspect would have been a disaster if I had already put the back of the top on the base.
5.) I built the bottom part of the bench and put it in the alcove in my bedroom before attaching the top. I did this mostly because I didn't want to carry that thing up 4 flights of stairs with the heavy top popping open. Once in place I threw on some wood glue, sat the top in place and used my nailgun to securely attach it. My mom was there with the paint roller to touch up a couple spots. Thank you mom, you always leave my house looking better than when you arrived :)