Being Prepared for Real Estate Investing

What are some best tips to help investors prepare for investing in real estate? I was talking with a property manager today and a great tip I took away from our conversation was to have space heaters or other heating sources if/when the heater in your rental properties go out so you don't need to pay ridiculous fees to have someone come out immediately. 

I would love to hear what tricks/tips you wish you'd know when you got started in Real Estate. Any and all advice would be appreciated!