Hey all, I've been playing HotS for a couple of months now and I remember how confused I was about the game coming from LoL as a Diamond player about priorities and what differences you should pay attention to on the game. Seeing that we'll have a whole heap of new players I've compiled a list of what I've observed.
- There are no items or skill progression but your talents can influence your character just as much. Explore other ways of building your character. For example, just because you're playing a squishy mage like Jaina doesn't mean you can't be tough without the right build and enjoy the battlefield from the front lines.
- You can cast many of your spells on buildings (e.g. shields or damage. No heals).
- Hearthstone often to heal up or mana up. I can't stress this enough. Unlike LoL, leaving your lane when you're a duo does not result in a gold or xp loss. Your lane partner may have to fend for them self for a while solo but it's better than you staying in lane with no mana or with low hp.
- Similar to point 2, Heal up and Mana up before objectives come available. Make sure you're not running into the mines or fighting for shrines at half your strength, you could easily end up losing objectives or worse, getting your team aced.
- Explore other lane combinations. The middle lane does not need to be the solo lane, all lanes gain experience at the same speed.
- Unlike LoL, pushing seems to be a lower priority. Not to say it isn't important but taking objectives are KING, stop farming creeps and run to that objective when it's up. There are a few exceptions but objectives should be your top priority most of the time.
- Mounts can get you around the map VERY quickly. If you see a battle break out on the other side of the map, chances are you can still get there in time to make a difference.
- There is no flash and no wards in this game so if someone is over extended, go with your team (or even solo) and punish them for a free kill. Likewise, you might want to think twice about going too far outside your gate if enemy heroes are missing, a three man gank from the jungle can kill you before you even make it halfway across the screen.
- There are no automatic calls for help with your towers. If their creeps are within tower range they can do whatever they want to you and your towers won't bat an eyelid.
- Feel free to leave your lane often to gank or even just to harass other lanes if you're in a duo. Even in a solo lane, if the enemy is over extending elsewhere, the lack of flash in this game makes it pretty easy to come up behind them with your mount and secure a kill.
- Farming in lane alone is pretty much the last thing you want to do in the mid and late game. Unlike LoL there are barely any advantages to farming, try moving around in a group to take objectives if they're up or gank the enemy if they're not grouped.
- Check your enemy's level constantly. You don't need to guess at the enemy's strength from how many dragons, towers or farm they've taken. Take extra care if they reach level 10 as well as 20 before you, they'll have their heroic ability or final talent and will probably squash you flat even with an advantageous engage.
- If you're lower level than the enemy try not to engage in an equal fight, if they're grouped around top, concentrate on taking objectives near the bottom. There are no wards in the game and limited vision control so avoiding the enemy and trading or even ninja'ing objectives before they can react can be safer and more beneficial than trying to force a fight in the jungle or in lane.
- There is blocking in this game. Be careful when your allies need to retreat and you're right behind them. Additionally, keep in mind that you can slow an enemy down by walking in front of them or even trap them in small corridors.
- Towers, Forts, Keeps DO NOT detect cloaked units. [EDIT: Thanks to JeffBlaze for this!]
- Cloaked units are still slightly visible as a shimmer and can be hit by skillshots and aoe spells. This will instantly uncloak them.
I hope this helps anyone else coming from LoL, or even those who aren't!.