Lets use some basic sizes that we see pretty often. 60" wide x 10 foot long.
1st Tip - As always PURGE. No doubt you have clothing you bought that's never seen the light of day. Chances are it's not your favorite, the style is not "IN" anymore or, it just doesn't fit properly. Either way, let's face it... there are always less fortunate people who would LOVE what you are no longer using! Consider making a local donation. PS: Get a write off too - it's a win win.
2nd Tip - Design your closet on paper. Once you have a design that looks good, your next step is to use a tape measure and some painters tape to mark your new closet design on the floor. The Painters tape removes easily and gives the visual you need. Now when you do this be sure you realize your clothing (when it hangs) hangs PAST the shelving. IE: Your clothing needs 22" from the wall to hang freely. So lets say you are going to install a closet system that is 12" deep or even 14" deep. Be sure to add a 2nd tape line wherever you'll planning to hang clothing. Lastly lets say you have as we noted above the closet is 60" wide.. so there is no way to install hanging on each wall .. since there would be no path in the middle to walk,
However, as you can see in the attached image our example closet has 12" deep shelves for shoes , handbags etc on the left and hanging on the right with shelves above. Since there's no hanging at face level you get "the feeling" of a wider closet (and it is easy to see the hanging clothing too since you are looking down on them) So in our example - your clearance is now 60 - (12 (left) + (-22) hang on Right) . So that's 60 minus 34 = 26" clearance. For most people this will work pretty well. The main point to remember is: when your closet is narrow be sure to place shelving on one wall and hanging on the opposite wall. In some cases you may need to place shelves for folded items, shoes , etc on Both Sides and hanging at the end on the closet & left and right of the entry door too. (when there's enough room)
3rd Tip: Decide if this will be a do it your self job or if you will be searching online to find up to 3 local companies that have a great reputation and have been in business quite a while. Naturally you'll want companies that also offer a Free Design Service. Next you'll invite each company to create a design based on your needs (do not show them your design - Yet) - Let's see how creative they are. Finally after you receive their designs and have had your any needed design changes done along with the updated pricing it's time to get started!
Lastly: Choose the Best Company to fit your needs and get your project started !
Good Luck !