Is it by following Jesus' commands, or is it a feeling towards God? How is it demonstrated?
I might be really selfish, I don't know if I have love for God.
We can love God for what He has done for us giving us eternal life, which everybody that accepts Jesus would love in this way, even the hypocrites that think they have eternal life.
But Jesus said that even the heathen know how to give their children good things, and the world will love their own, and that is because the world will choose who they love based on the person's character, and what they believe.
To truly love God is to love His character, which He represents goodness, and holiness, and truth, as well as loving Him for what He has done for us.
That is why the Bible says herein is the love of God, that we keep His commandments, and His commandments are not grievous.
That is why Jesus if a person does not do the things that He says the person does not love Him, but the person that does what He says loves Him, and Jesus is a sinless man that did good.
The hypocrites that engage in sin, and hold unto sin, and some thinking they are alright with God despite their sins, do not love God for His character of goodness, which God said be holy for I am holy.
They do not want to be like their Master Jesus in representing goodness, and truth, and Paul said love does not think an evil thought, and does not rejoice in iniquity, but rejoices in the truth to abstain from sin by the Spirit.
And love is greater than faith.
Jesus said whoever is ashamed of Him then He will be ashamed of them, so if they do not represent goodness, but want to engage in sin, then they are ashamed of their Master who hates sin.
The hypocrites love God for what He has done for them, but they do not love God for His character of goodness, and truth, by them holding unto sin, for if they loved God they would want to be like Him.
2Ti 3:4 lovers of pleasures more than lovers of God;
2Ti 3:5 Having a form of godliness, but denying the power thereof: from such turn away.
2Ti 3:7 Ever learning, and never able to come to the knowledge of the truth.
There are millions of people that are not led of the Spirit, and will not let go of all of the flesh, but hold unto sin and think they are alright with God, and never come to the truth that sin separates them from God whether they confess Christ or not, and do not represent the character of their Master Jesus.
1Jn 5:2 By this we know that we love the children of God, when we love God, and keep his commandments.
1Jn 5:3 For this is the love of God, that we keep his commandments: and his commandments are not grievous.
Joh 14:15 If ye love me, keep my commandments.
Joh 14:23 Jesus answered and said unto him, If a man love me, he will keep my words: and my Father will love him, and we will come unto him, and make our abode with him.
Joh 14:24 He that loveth me not keepeth not my sayings: and the word which ye hear is not mine, but the Father's which sent me.
Luk 6:46 And why call ye me, Lord, Lord, and do not the things which I say?
Hypocrites that enjoy the world like the world enjoys it, that love money, and material things, and neglect the poor and needy, that engage in fleshy pleasures, all the while thinking they are right with God, and some making an excuse that sin does not affect their relationship with God, and they cannot abstain from sin, even though the Bible says if they hate sin, and do not want sin, by the Spirit they can abstain from sin.
These people love God for what He has done for them, but do not love God that His character is goodness, by not representing goodness by their hypocrisy.