The first step, always, is to read the thing you're summarizing or paraphrasing. You can't compress the information (summary) or make it more accessible (paraphrase) without having read it--and, ideally, more than once. As time permits, read the first time just to read through and get an idea of what's going on. Read again to make or take notes, pointing out what's important and what confuses. Another re-read or two will reveal more of those, as well.
For a summary, it'll be enough after the readings to begin drafting. The first sentence in a stand-alone summary should identify the thing you're summarizing. The next sentence should point out its central point. Following sentences should note the important points in the thing you're summarizing--in the order they appear. Chapter titles and section headings will be give-aways for this, but for pieces that don't have them, go back to your notes about what's important.
For a paraphrase, you'll want to look into the things that confuse you, doing research until you understand them. (You can't make it more accessible if you don't understand it.) Once you're not confused, draft the paraphrase. If it's a stand-alone thing, you'll open the same way as you do a summary; the first two sentences will be the same. After that, though, you'll want to break down the major ideas in the way that makes them easiest to understand--which may not be the order they appear in the thing you're paraphrasing, and which may be longer than the original.