The main things a president actually does are as follows, I also believe people should vote based on how they believe the candidates will do these things.
1. Commander of the military.
I believe both Trump and Clinton will use the military more than necessary, and in a way that creates more enemies rather than defeating or making treaties with enemies. Also continuing the trend of spending more on the military than the next 3 biggest militaries combined. I believe Gary Johnson would do more defense than offense, and that he will stop increasing military spending.
2. Making appointments and nominations.
I believe this one will be fairly straightforward with Hillary choosing progressives, Trump picking conservatives and Johnson picking socially liberal fiscally conservative people.
3. Executive Orders
I liked Obama's executive orders for the most part, and if Hillary does similar, I'd be okay with that. But I like Johnson's strategy more, he says he will get rid of the NSA with an executive order, and leave the rest of the law making up to Congress the way it should be. I'm scared of Trump executive orders, I'd expect things like not allowing certain people into the country, more surveillance of muslim religious people/buildings etc.
4. Vetoing/passing bills
I believe Clinton would increase spending and decrease freedoms by passing bills, I believe Trump would increase spending and decrease freedoms by passing bills, and lastly, I believe Johnson would veto bills.
5. Submitting initial budget, approving or vetoing final budget
I believe Trump and Clinton would be okay with increasing spending, they'd both submit budgets with large spending increases and approve budgets with large spending increases. While Johnson would submit a balanced budget and veto the crap out of spending increases.
6. Dealing with other countries and representing ours
I think Trump would be the worst president ever when it comes to this, he will get into arguments with other foreign leaders and drag our countries name through the mud some more. Clinton and Johnson would probably both be mediocre.