This page covers basic and generic tips for giving good talks. You should also read about the Punch Line Method for my specific strategy in giving talks. Since there are many tips out there already, I mostly have links to other tips, and a small check list to catch basic mistakes.
As a general advise, don't be presenting your slides. You have a talk that you want to give, and slides are their to help you deliver the talk. If you are only reading your slides, the audience might as well read them themselves, and not listen to your talk.
Here are some additional tips on how to give academic talks:The second link is a bit outdated. It tells you to write your slides (transparencies) by hand, but this is not really possible anymore.
You cannot give a good talk unless you practice it. Make sure not to follow these tips: How to Give a Bad Practice Talk. In particular, if you have just finished your slides 5 minutes before your practice talk, then you are immediately disqualified to give it in my opinion. It is disrespectful of the attendees of your practice talk if you hadn't had the time to fix basic things in your talk on your own.
There are many things you can do before you give a practice talk to some group. Below is a minimal check list that you can do by simply going over your slides to avoid basic issues in them.
You should be answering yes to the following: