Gary Chapman's book The Five Love Languages describes these methods of showing love. Learning to use the language that is most effective for a particular person is one important way to strengthen one's relationships, both physical and spiritual. While each person responds best to one or two of these languages, God is not limited by human needs and can appreciate any of the five. Some actions cannot directly be performed on a non-physical being, but, using the principle of Matthew 25:40, performing them for anyone is the same as performing them for God.
This category might be the most important of all of them. Time is something that can never be recovered once spent, and spending it speaking to or learning from the Creator is always worth it. Like any relationship, time must be devoted to God for one's spiritual life to flourish. Taking time throughout the day to speak to God greatly strengthens one's ability to follow His ways.
In the context of worship, this category can also be called praise. For many good examples of praise, read through the Psalms. Praise can include singing hymns, giving thanks in prayer, or telling someone about an answered prayer.
Giving something directly to God can be called sacrifice as well. This can be tithes or other monetary sacrifices, but it can also include giving up or changing an aspect of one's life to conform to God's ways. Of course, giving to someone else to meet their needs also counts.
This might also be called good deeds. Service in general is a very broad category that can not only include serving in church, but also anything else that does something for another person. This might be cleaning the house for one's spouse, making a child's favorite dinner, or doing extra on a project at work.
Although this is the primary category that cannot be performed directly for God, people need physical touch to thrive, and so any touch performed for the benefit of someone else also honors God. Remember that the next time you give someone a gentle hug.
Learning to perform these methods of showing love for both God and man will help one to become a more loving person overall. Keep in mind, however, that while all of these actions are beneficial both for the doer and the receiver, none of them can have any effect on one's salvation. Also, unlike people, God is not dependent on receiving these things to be happy. The doer is the one who is benefited the most by doing these things for God or others.
For more information, read more about this book and other recommended books on building relationships.