It might be said that the "spirit" of all our actions as Muslims is, or ought to be, our love for Allah swt. It brings coolness to the eye (is that a fair way to use that idiom?) and motivates us to increase our acts of worship.
Allah, the Generous, has given us the gifts of this life: our hearing, and sight, all the faculties we need to survive in this world. The love of everything else in this world should emanate from the love of Allah swt. He endears Himself to His servants, doing things to make us love Him, so the love is (or should be) mutual.
Allah swt loves for us to turn to him after we commit sins.
Anas b. Malik reported that Allah's Messenger (may peace be upon him) said: Allah is more pleased with the repentance of a servant as he turns towards Him for repentance than this that one amongst you is upon the camel in a waterless desert and there is upon (that camel) his provision of food and drink also and it is lost by him, and he having lost all hope (to get tbat) lies down in the shadow and is disappointed about his camel and there he finds that camel standing before him. He takes hold of his nosestring and then out of boundless joy says: 0 Lord, Thou art my servant and I am Thine Lord. He commits this mistake out of extreme delight.Naturally our hearts incline towards a love of Allah. All provision, tranquility, and peace in our hearts is a favor from Allah swt. And to love Allah swt more fully we must understand the bounties He has given us.
We can love Allah swt through his names: the Forgiving, the Merciful, the Generous, the Protector, the Gentle, the Clement. Only believers can truly love Allah swt, as the disbelievers turn away from Allah and take partners in what they love. That's why believers love Allah most.
5:54 O ye who believe! if any from among you turn back from his Faith, soon will Allah produce a people whom He will love as they will love Him,- lowly with the believers, mighty against the rejecters, fighting in the way of Allah, and never afraid of the reproaches of such as find fault. That is the grace of Allah, which He will bestow on whom He pleaseth. And Allah encompasseth all, and He knoweth all things.And who truly believes?
The Prophet said, "By Him in Whose Hand my soul is, (you will not have complete faith) till I am dearer to you than your own self."And of course Allah swt has more right to be loved by His servants; he provides for us, has mercy on us, and forgives us for our sins. Allah loves His servants but does not require anything from us.
How can we love Allah swt?
1) Reciting the Qur'an and reflecting on its meaning. If you love someone, then you love to read his words--the letters he might have written you for example; if you love Allah then why wouldn't you love to read His words, the Qur'an? The Qur'an is addressed to the believers, who should listen attentively to the words of Allah swt. And reciting even a letter of the Qur'an earns a reward. In fact the Qur'an will be an intercessor on the Day of Judgment for those who recited it. But regarding the topic at hand, our love for Allah swt will grow with reading the Qur'an.
2) We should draw nearer to Allah swt by performing extra voluntary acts of worship (nawafil). Acts of worship are not just rituals, but when done properly they affect our hearts. Allah swt says that His servants can draw nearer to Him first by performing obligatory acts of worship, then voluntary acts of worship. This includes extra prayers and fasting.
3) To continue remembering Allah swt with the tongue, heart, and actions. Remembering Allah with the tongue is even considered an act of charity, something for which we will be rewarded, but it is also a way to increase our love for Allah swt.
4) By giving preference to what Allah swt loves, instead of what we prefer. We should not admit any partner in our love for Allah swt--when we act on our own desires in preference to what Allah loves, then we are in a way granting ourselves more importance and love than our Lord.
5) By witnessing the names and attributes of Allah swt and to feel them in the heart. In the Qur'an, Allah has shown us His names, His attributes, that He is Forgiving, and Merciful, Gentle, and Loving. That He is near to us and always listening when we supplicate to Him. So we should call on Him often and know He is listening, that He is All-Hearing. And He is Oft-Forgiving so we should beg for His Forgiveness.
6) By witnessing the favors that Allah swt has given us.
7) By humbling our our hearts in front of Allah swt. Our love for Allah swt can increase when we understand that we are His servants, and that He is Merciful. Humility allows us to fully understand the many favors Allah swt has given us, and to appreciate them without arrogance and that appreciation can foster more love for Allah.
8) By increasing time in privacy with Allah swt, by asking forgiveness in the last third of the night. Devoting this extra time when we might like to be sleeping to Allah... He descends to the lower heaven at this time and wants to forgive us, we only need to ask.
9) By sitting with those who are truthful in their love of Allah swt. The comparison is of sitting with a seller of perfume vs. a blacksmith, and how the presence of one creates a different and more pleasant effect than the other.
A condition for loving Allah swt is that if you want Allah swt to love you, follow the Prophet (saws).
Signs (proofs, tests, etc) that we love Allah swt are that we love to meet Allah, that we give preference to what Allah loves and avoid following our whims, that we avoid disobeying Allah. Love and obedience of Allah swt go hand in hand--sins are not proof someone does not love Allah. Other signs are that we love the words of Allah and the messenger, and that we love the people of faith.
Allahumma musarrifal-qulubi, sarrif qulubana `ala ta`atika (O Allah! Controller of the hearts, direct our hearts to Your obedience).
These are some of my notes from a recent lecture... I'm not sure of the original source... please notify me for any corrections.