As you should know, maintaining relationships takes time and investment, whether they are platonic, familial, romantic, etc. Most of our energy and resources go into our primary relationships which we seek to cultivate and maintain. What you define as your primary relationship is up to you. Christians, however, are called to develop a relationship with our Father as our primary, the one we put above and before all, and it requires just as much attention.
If you are unsure on how to develop a strong spiritual relationship, you can take some clues from your earthly ones because what is most important is to address the needs of the other and to be attentive.
Communication is important in all relationships, and regular communication is ideal. It means a believer must stay in contact with God and talk to Him regularly. You must also listen just as much or even more than you speak. This means praying because prayer is how we communicate with Him. You text your friends. You talk with your peers, and you call your significant other religiously at times. How often do you stop and talk to God?
He too wants to talk with you, and He deserves as much time. You can speak with Him at specific times or on the go. It hardly matters when or how long. He wants your acknowledgment. It just matters that you reach out. Thank Him for what He has done for you like you would anyone else. Ask for His support. Request His help, but don't demand it, because it's rude, and you shouldn't do it to anyone.
Another key is making time. One way people make time for those they care for is by planning dates. So, make a date with God. Pick days or times where you dedicate all your attention to Him. Turn off your devices and block out all distractions because it's just you and Him. Dates are all about talking and getting to know one another. Prayer comes in here as well, but this is the time you open yourself to Him, and you, in turn, learn more about Him. Tell him about your world, and be straight with Him because He already knows all your innermost desires and struggles.
However, just like we prefer when people trust us enough to confide in us even if we already know something, He too wants you to tell Him what is on your mind and in your heart. What worries you? What are your dreams? What do you wish for? In return, to learn more about Him and His desires, a Christian is gifted a text all about Him and His works. Take this time to read the Bible and meditate on His Word. Be curious, ask questions, and seek answers. Get to know Him as much as He knows you.
As much as you should get to know Him, you should also get to know His friends and family just like you would in any other relationship. These are His body, your fellow Christians. They love Him just as much as you do, and He loves them. God made us to be a community, to support and guide each other. We are rarely strong enough on our own, and we need the support of others to get through life and, especially, to advance in our spiritual journey.
Your Christian fellows are who you go to when you need someone to talk to, whether you are so excited by something He has done for you or when you feel the least bit slighted. They are your mediators and intermediaries. They keep you on the right track and do their best to keep you from doing something you might end up regretting. God wants you to know those He favors and loves. They are as much your family as they are His, so get to know them.
There is much more involved in developing and maintaining a relationship, and those are things you should seek out from your community, your research, or your own wisdom and discernment. One more important thing is to show Him the love and respect we all value and He deserves. As you wouldn't or shouldn't deny or reject a friend or partner to save face or avoid social stigma, you should not deny Him.
If you profess to believe in the Savior and our Father, you are stating you want a relationship with Him. You should be proud of and secure in your decision and seek not to hide or cover up your Christian identity, for he says, "But whoever denies Me before men, I too will deny him before My Father in Heaven" (Matthew 10:33). You wouldn't want someone to reject or disown you in a relationship, so you shouldn't do it either.
Be blessed, remain firm, love your neighbor, and have faith, for He will provide all your needs.