If you want directions to get to a certain place, you have to admit that you don't know the way yourself. You have to be willing to accept that what you thought was the right way may not actually be! If you're determined that you already know the right way, you won't listen to advice. It's the same with making decisions. If you want to know God's will you must be willing to accept whatever His will is. And often (but not always) it's not we would choose.
For my thoughts are not your thoughts, neither are your ways my ways, saith the LORD. For as the heavens are higher than the earth, so are my ways higher than your ways, and my thoughts than your thoughts. Isaiah 55:8-9
I think this is the most important of all. Don't make any decision without first praying about it. A number of times in the Bible it says that David enquired of the Lord. And when “David enquired the Lord answered.
The Bible also says In all thy ways acknowledge him, and he shall direct thy paths. Proverbs 3:6 If we sincerely pray about our decisions, God will show us the right way to go.
Don't depend upon feelings
Feelings don't always tell the truth. Feelings aren’t reliable. Feelings are very changeable. God's will is often something we don't 'feel' like doing. And what we do 'feel' like doing is often not God's will!
Seek God's will through His Word
Thy word is a lamp unto my feet, and a light unto my path. Psalms 119:105
When you have a decision to make and you are praying, sometimes God uses a verse in the Bible to give you wisdom. There have been many times that verses have jumped out at me and I know that it is God speaking to me about this particular decision. There is so much wisdom in God's Word and such good principles. God's will won't contradict His Word.
Note providential circumstances
When I first started getting to know my future husband, I found it quite confusing sometimes. How did I know if he was the right one? I remember one morning thinking, How on earth do I know? But that day two things happened, just little things, that confirmed that I was going in the right direction. They were like markers along the trail. They were providential circumstances. God can use people, open or shut doors (opportunities), sermons, things we read in books, phone calls, emails, etc. as markers along the trail.
Don't rush into anything. Take time to pray about it and think it through. The more important the decision, the more amount of time.
Ask for advice
If you have godly parents, ask them what they think. You will still have to make your own decision, but you're parents have more life experience than you do. And God may use them to help you know what the right decision is. They might not know what you should do, but at least they may warn you if they think it's not a good idea. I remember when I got my first letter from my 'then future' husband. I showed it to my parents and asked them what to do. They told me it was my decision, but they also didn't have anything against him. If they had, that would have been a red flag.
If you don't have godly parents, ask your pastor or someone else that you know walks with God. I am married, so often if I have a big decision to make I ask my husband. First of all I pray that God will give him wisdom. Then usually if he thinks it's a good idea I'll go ahead with it. If he doesn't I'll usually decide not to.
The way of a fool is right in his own eyes: but he that hearkeneth unto counsel is wise. Proverbs 12:15