Step 1: Brush Hair
Make sure you brush the hair so that there aren't any tangles in hair. If there are tangles it will be difficult to braid and you are prone to make a mistake and start over.
Step 2: Part Hair
Separate the hair into two different strands and try to get them as even as possible. Make sure you start your part at the middle of the head.
Step 3: Begin the Braid
Now you take a strand of hair from the right side (you can start on any side I prefer the right) outside piece. Then bring that strand to the left side adding it to the left side. Repeat the same thing on the left side.
-There are many sizes you can have for a fishtail braid and how you determine that is by the amount of hair you grab at the beginning. Try your best to keep grabbing the same amount every time you grab a strand this is how you get a clean, correct, braid.
Step 4: The Pattern
When braiding pull both sides to ensure your braid will be tight, if you do not do so then your braid will be loose and might not stay. However some girls wear loose braids as a style so it's up to you how you want your braid to look. Keep the pattern going all the way down to the very end.
Step 5: Finish
Once you have braid you fishtail to the desired length, obviously, seal it with a hair-tie of your choice. Enjoy!!