Do I need to render the video before the final render in the output format I want?
As I add titles and effects, I'm currently rendering the video - primarily because it's easier for me to work on the project if I can watch smoother video. At the end, I go to the share tab and render the project in the final format that I want e.g. mpg, etc.
I'm trying to see if I can speed up my workflow by skipping the intermediate renders before the final one. Or do I still need to keep rendering to prepare the footage for the final render?
No you don't. You don't really even have to render while you are working on the project.
Note that when you render only the area under Work Area Bar is rendered so, if you need to render an area because you want a better view of a transition or effect, you can set the Work Area Bar to cover only that area of your timeline, and then PRE will render only that area.
Insanity is hereditary, you get it from your children
Remember, though, that the video WILL have to be rendered at some point though -- and, if you don't do it, the program will have to when you output your video.
So you really don't save any time by skipping the step. You just postpone the inevitable. (And, as Neale says, you'll also see decreased performance of the program if you've got a lot of unrendered files on your timeline.)