This will be kind of hard to explain...
When your braiding, the bit that you have just added to, I let it lay down their neck and hold the other two in one hand, and pull the one you just added to through so it's super tight, then move on to the next one. After a bit of practise I can get braids like that top one...That probably didn't make sense, it's something I normally show people!
Also try standing on a bucket and braid from over the top of there neck, it makes for a tighter braid.
Let me knwo fi you didn't understand :]