Here are the basic 3 steps to come to a good presentation slide. And for 2, you do not have to be a stellar designer to get them right. For step 3, you can use my presentation design app SlideMagic)

1. Decide on one message, one message only. Here is where most people go wrong: they try to put more than one idea on a slide. Too many things to grasp at once, too much content/clutter on the slide. Only if your message is: "There are 15 reasons why you should stop smoking") might you consider a list of 15 small bullet points.
2. Decide on a basic slide structure. The only structure most people use is the list. But there are other (simple) ones that you should consider. A contrast (box on the left, box on the right), a ranking (bar chart), an overlap (Venn diagram), pros and cons (table), cause effect. They are not that hard to put on a slide.
3. Get the design right. Now, here it might be trickier for the layman. Fixing alignment, proportions, grids, colours, white space, etc. etc. SlideMagic users won't have to worry much about this, for everyone else, here are some of the guidelines I have implemented in SlideMagic:
   1. Everything lines up 
   2. Everything lines up according to a grid
   3. Calm colours: one accent, lots of shades of grey
   4. Safe (sans serif) font
   5. Slides look similar in one presentation (positioning of titles, margins, etc.)

There is no reason to get 1. or 2. wrong, and you can learn 3. over time.

Art: Silver Landscape, Photocollage by Gordon Rice