For short stories, I use a rough point outline to plan it. Just a list of plot points, Character A goes into the store and sees Character B, Character C asks Character A to get .....
For longer stories I use a modified version of the mind mapping technique, it's also called spider or web I think. It's easier done on paper, but if you have MS Project or similar, or are familiar with MS Word you can do it on the computer. http://www.wikihow.com/Make-a-Mind-Map
I mind map the main character or main theme on one page, labeled A, and write out the events that happen to that character or create the theme, with each labeled A1, A2, A3 etc. Then each smaller event or character gets their own page B, C, etc, with the details of the event. When it's time to write the story, I play with the smaller events until I get them in the order than makes sense. Some events make it into the story, others don't.