No reason to have bad hair days in your virtual life! The way other users interact with your avatar depends greatly upon outward appearance. You want to lose that noobish look ASAP! Hairstyles play a big part in a great look for your avatar, and you really can't get it right with the built-in appearance tools.
Step 1: Go ahead and try the built in sliders...
There's no harm in playing with the sliders. It is actually quite fun. Just remove the starter hair that came with your avatar by right mouse clicking on it and and choosing "detach". This will leave you with a bald head. Then, right click your avatar, and choose "appearance". Your avatar will assume a still pose. Choose the "hair tab" and have at it for a bit. If you prove me wrong by creating something flattering, do send a snapshot of it along to me. But I'm betting you will grow weary of this game after a while and be ready for some other options.
Step 2: Shop for prim hair...
The quickest way to upgrade your avatar's appearance is with some great prim hair. It comes in thousands of styles and colors priced at around L$100 to L$250 for one style in a range of 6 or so colors. Almost every store allows you to try a demo version which you purchase for L$0. To find places that sell hair, look in search using keyword "hair".
Prim hair is made up of many small pieces called "prims". Some hairstyles have hundreds of prims. Some hairstyles are rigid and some are flexible, meaning that they move when you move. This gives a more natural appearance. Flexi or not should be indicated on the display in the store.
Some stores offer one or more styles for free as a promotional item. There are also some non-commercial locations, like orientation areas, that offer free prim hair. IM me, Thynka Little, in-world to say you saw this on Instructables, and I will give you my current list of freebie places.