For most people this would not be an issue since they follow a master or religion which had a master and now has some method or dogma. The master when alive, is God personified. They are the son or daughter of the most high, a direct representation. The power housed in them is the same as the almighty; the outer form is just outer clothing for that power to be accepted in whatever culture the master was born in.
This is how God creates affinity with us so we can trust God; its how we are taught and shown the way home; back to Heaven. So, with this physical persona, we can develop a trusting relationship; especially when the master is alive. It is in fact the foundation of eastern spirituality, to devote to the guru. There is a saying, if both God and the guru appear, bow down to the guru. Why, because the guru is responsible for taking us to God.
If the master has long passed away, like Jesus or Buddha, it’s a little more difficult to develop a trusting relationship but not impossible. There is a sort of bad joke, “better to have a dead master than living because dead ones cannot scold us and tell us all the things wrong with us “
If we are atheist or just don’t have an image of God we can relate to, then you can also use nature or a person you respect and love deeply. See the God within them. If you do not want any image, then think of the absolute form of God – infinite, vast, endless, without a beginning or end.
So now we have a vision of what God is – this, by the way, is only for the mind to accept, God has no form.
We test God by asking for, and expecting help when needed and proof of a connection. If you ask for a million dollars, 5 Ferrari’s and the Presidency of the USA; it may take time, like a few lifetimes, so be patient. But if you ask simple things, like to help you get through a crisis or some vision, these are easy to arrange.
By asking God, you are using God; it’s your birthright. Parents are there to be used as pillars of support, and even for material support when needed. When we practice spiritually, God becomes our employer. If your boss gives you money for doing 9-5, why wouldn’t God reward us for striving to know the truth and glorify creation!
When nobody else can help, rely on God. Remember God always. As you are given proof, little by little your faith will improve until you have love and trust in God. Real trust, formed through a true loving relationship. Not just something a priest told you.
As to whether you trust fully or partially, it’s up to you. Your Dad would not mind, so why would God? Real love is unconditional, even if we betray Gods trust from time to time – its OK; Just keep trying; our Father is already very happy we try our best.