I'm assuming you mean 'proper' dinner party as opposed to relaxed dinner with mates?
Make sure you pitch your cooking at an appropriate level to your experience.
Shop the day before, or by mid-morning, latest.
Make sure at least one course can be prepped the night before or that morning.
Serve a cheese course - don't put it on a board for people to hack at, do it civilised - a small 1-2" square of 4-5 varieties, spanning blue, creamy, hard cheese, and a couple of wild-cards, with a couple of pieces of thin rustic bread or a 2-3 oatcakes, arranged prettily on individual plates with sliced apple or figs or some such. You can do all the slicing before hand and plate it up in minutes, and it's a nice lingery course to include for no more effort than shopping and chopping.
Have 3-4 small courses, rather than a heaped platter of main course and pudding.
Relax, don't come to the table explaining problems or delays, just pour more wine.
Don't wear pale colours unless you're very tidy, or someone else is doing the catering.
Take some real effort over presentation - I have offered spectacularly ordinary chicken liver pate which received more praise than its worth due to its neatly moulded shape dressed nicely with leaves, and drizzled dressing, and curls of lemon zest.
My dinner parties are either well-oiled machines or shrieking disasters, no middle line - I agree with a glass of something interesting at the start to set things off on the right foot.