One starts in one corner, clearing a square about 3' to a side. Then you can stand back and see that something was actually done. Do one square at a time, clearing all junk-plants out, then putting down a layer/6 sheets of wet newspaper around the remaining plants/shrubs and topping the paper with 2 or 3" of mulch. Then it's obvious that you really are done with it! I recommend starting with the corner nearest your front door.

The other way is to do it in layers, pulling the biggest weeds first and then going back and pulling the middlin' sized and then getting up close and pulling out the tiniest. Works, but you don't really see much improvement until it's all done. After the weeds are mostly or all gone, do mulch heavily, else you will find more weeds busy growing up almost as fast as you pull them out. Whichever, don't try to clear everything all at once unless you are very young, in excellent physical shape, and have a lot of help. ;)

While you are taking a break from pulling weeds, do a search in this forum for "new bed" or "lasagna" or "soil". Lots of suggestions on how to start. You may want a camera to take pics of before and after. Also good to take pics of anything you aren't sure about, it would be a shame to pull up a nice perennial just because it wasn't recognizably in bloom; post it and folks like to figure out what you've got.

Can you could give us more help on sizes of areas you'd like to plant things and what things interest you (flowers? vegetables? herbs? fruits? perrenials? annuals? shrubs? trees?). We'd be better able to help you.

In the meantime, take a look at what neighbors have planted that you like and dislike and visit gardens and garden centers.