Kindred's unique feature is its marks. To play well with it, you must understand how they work.
First, all of its skills scale with marks.
Your Q gives additional attack speed based on the marks, your W deals damage based on the target's current additional life, and your E deals more damage based on the target's lost life.
If you have 0 marks, it will ALWAYS spawn on the scuttle (the 2 scuttles at 3:30 are random, it can spawn on any). If you have from 1 to 3 marks, it can spawn on the scuttle, raptor, and gromp of THE OPPONENT JUNGLE. If you have from 4 to 7 marks, it can spawn on the OPPONENT wolves, krugs, and red/blue buffs. If you have 8 or more, it only spawns on objectives (it doesn't spawn on voidgrubs).
If your mark is made (by you or someone else), it takes 15 seconds to disappear from the map and another 30 seconds to spawn somewhere else, totaling 45 seconds for another mark to spawn. With that in mind, if your mark was on the gromp, someone else made it and the enemy raptor is about to respawn, and the scuttle was made recently, the only option for your mark to spawn is on the enemy raptor's next respawn (taking into account that you have between 1-3 marks).
In addition, you can mark an enemy player, if you get an assist on their death or get the kill, you earn 1 mark. It's important to know that, when you click to mark a player, the mark takes 8 seconds to actually leave the target marked, so if you kill them in less than 8 seconds after marking them, your mark won't count and you'll need to kill them again. It's also important to know that when you click to mark someone, that person is notified, so if you mark them too far before starting a gank, it's very likely that the enemy will retreat and you'll lose the gank. Many times, I gank without marking the target, since it's better to at least get a kill than to leave with nothing. There are also ways to play mind games with this. If you don't want to go to a lane but you see that your laner is being pressured a lot, you can try to mark the enemy laner to see if he retreats a little and give your laner a break. Normally, as a jungler, you want to see the game up to 1:30 minutes in the future. For example, you finished your full clear and recalled at 3:50. You should already know what your next steps are by 5 minutes into the game. If you want to do 2 more camps and rush a dragon, if you want to invade, etc. With that in mind, something useful to do with player marks is to mark the player you want to gank in 1:30/2 minutes.
The mark spikes are: 4, 7 and 10. At the 4th mark you gain 75 additional range (you get 575), after that, every 3 marks you get you gain another 25 range (600 range at the 7th mark, 625 at the 10th). So your overall spike will always be every 3 marks after the fourth.
KEEP IN MIND THAT THE FOURTH MARK IS THE MOST IMPORTANT. Always play your game trying to get the marks, but don't die for them, the only mark worth dying without getting a kill is the fourth. Other than that, sometimes it's worth dying in a kill trade while getting a mark. GLHF