Presentations should be approximately 15 minutes to allow ample time for questions and discussion.
Do not use slides. Only exception is to show pictures and video (if the paper cannot be understood without). Text and equations should be written on the board. The purpose of this is to encourage high quality presentations, to give practice, and to keep up the attention of everyone.
Focus on what's important. Present the paper as if everyone skimmed it but forgot it, or didn't understand. This means that you first present (a) the problem that the paper solves, (b) the general approach, and (c) one or two key details about the approach. Of course, the specifics will vary with papers. For every algorithm, be clear about what are the inputs and what are the outputs before describing the algorithm.
Schedule a time to meet with me at least one day before the presentation. I'll try to help you organize the talk and answer any burning technical questions.
If you don't have much speaking experience, this is good practice. It's worthwhile to practice your presentation before you give.
If you don't present on that day: Hand in a short ``review'' (a few sentences, does not need to be polished) about a paper of your choice from that day. Discuss things that you like, don't like, or otherwise find worth mentioning about the paper.