Be organized on the front end. Have your plan and stick to it. Changes, indecision, and unpreparedness cost you time and money plus make your contractors frustrated. Do them a favor and be organized and decisive so they can get things done as efficiently as possible. Happy contractor, happy investor.
Only pay for completed work. No upfront deposits to contractors. It's OK to pay for materials for certain subs, it is not their job to fund your project but no labor payments.
Make sure you are covered with proper insurance. A lot of liability in this business.
Find a balance between design and budget. If you're not good at design it's OK. Don't try to be original, Google is your friend. Find something you like and simulate the same style with your selections as close as you can. Copy the paint colors, etc. Don't make things harder than they need to be.
You don't have to be an expert on construction but if you plan to project manage and over see the GC and/or subs then you need to learn the basics or you are going to get kicked around in this business. The stupid tax can be pretty hefty.
Find your strength and hire/partner for the weakness. Half the watermelon is better than the whole grape.
LVP is your friend.
Don't chase deals on materials constantly. You are wasting time. Look to make it easy for to get materials organized and to the site. The service a supply house provides is most often worth the extra price you may pay because it saves you countless hours. If you are going to use a box store stick to Home Depot, sign-up for a pro account and take advantage of their backend office for Pro's, it is very robust and will make your life easier.
Use text to confirm for order purchases or give your PM a HD/CC with a set limit.