Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This build is a great harassing build for Nidalee. It is not recommended for people who have never played Nidalee before. This is the third build I've tried for her and by far my favorite with good survivability (assuming you don't charge in) and excellent harassing ability.
The runes are pretty self explanatory... Quintessence are movement speed so you can get in and out quickly and combined with the dodge from the seals it makes her aspect great for running or chasing. The marks and glphs then just stack ability power so that you can pile up both her damage and heals.
After playing with the masteries for awhile this is what I came up with. To keep Nidalee's survivability up (because she is normally quite squishy) your going to put 21 of your points into defense so that you can get that 4% damage reduction. At the same time evasion and nimbleness are a huge help when you use your aspect because of the extra 10% dodge. In the attack tree take the extra ability power then cooldowns and penetration because it helps a lot with your Javelin Toss.
The items I picked because they stack real well with Nidalee's Javelin Toss. You end up getting an extra 40% magic penetration early game which helps with tanks a lot. You also stack up on ability power and reduced cooldowns for your Javelin Toss and Primal Surge. You don't need to worry about mana if you bring Clarity with you and between that and Will of the Ancients spellcasters on your team will love you. Throughout the game assuming you don't constantly die and lose stacks on Mejai's Soulstealer I usually go around hitting most caster's for about half their health with Javelin Toss. At the end with bonus ability power you can also heal for over 1000 with Primal Surge.
Simple enough priority is on Javelin Toss for harassing with Primal Surge as backup to help allies or keep yourself in the field gaining experience. You want to grab Bushwack before you get your aspect just so you can Pounce when in cougar form.
Exhaust to slow/weaken enemies for chasing/running with Clarity for mana reserves early game.
Once again, learn how to harass with Nidalee before using this build. If you don't know what your doing you can't stack Mejai's Soulstealer and that's a big loss in ability power/cooldowns if you can get it all the way. Simply harass with your Javelin Toss while staying out of direct combat and using Primal Surge to heal yourself and allies when needed. Bushwack is great for keeping track of enemies movement in the bushes so try to use it whenever possible. While this build focuses less on the Aspect of the Cougar it is still has it's benefits. Two of the skills get benefits from your ability power which makes it great for clearing mobs quickly or chasing an injured enemy. Also in conjunction with her passive ability and Pounce she can move through the jungle to get away very quickly especially if Nimbleness is triggered.