Al-Fatihah 1:5

The fourth verse اِيَّاكَ نَعْبُدُ وَاِيَّاكَ نَسْتَعِيْنُ : “You alone we worship, and from You alone we seek help” has a double aspect, one of praise and another of prayer. A man's life is subject to three states of time -- past, present and future.
The first two verses of the Surah, اَلْحَمْدُ لِلّٰهِ رَبِّ الْعٰلَمِيْنَ (All Praise belongs to Allah) and الرَّحْمٰنِ الرَّحِيْمِ, (the All-Merciful, the Very-Merciful), remind man that, as far as his past and present are concerned, he owes everything to Allah alone, for it is Allah who created him out of nothing, endowed him with the best form in the universe, and with reason and intuition, and continues to sustain and nurture him in the present. The third verse: مٰلِكِ يَوْمِ الدِّيْنِ (Master of the Day of Judgment) tells him that in the future too he will have to depend on Allah alone, for on the Day of Requital one cannot possibly have a helper other than Allah. The three verses having made it clear that man is totally and absolutely dependent on Allah in all the three states of his life, it logically and naturally leads to the conclusion that Allah alone is worthy of being worshipped, for in Arabic the word ibadah (worship) connotes showing the utmost humility and submissiveness out of an intense respect and love for someone, and such an attitude of willing self-abasement cannot justly be adopted towards anyone except Allah. So, the phrase: اِيَّاكَ نَعْبُدُ (You alone we worship) expresses this very natural and logical conclusion. And once it has been understood that there is only one Being who can satisfy all our needs, it is equally natural and logical to turn for help in everything to Him alone. Hence the phrase اِيَّاكَ نَسْتَعِيْنُ (to You alone we pray for help). Beside these two aspects, the fourth verse has another dimension as well. It teaches man not to worship anyone except Allah, not to consider anyone else as being really capable of satisfying his needs, and not to beg anyone else to satisfy these needs. It does not, however, go against this principle if, in praying to Allah, one mentions the name of a prophet or a man of Allah by way of a medium (wasilah) for drawing the mercy of Allah upon oneself.
It may also be noticed that the phrase: اِيَّاكَ نَسْتَعِيْنُ (to You alone we pray for help) does not mention the purpose for which help is being sought. According to most of the commentators, it generalizes the idea of the request to cover everything from acts of worship to all possible worldly or other-worldly concerns.
Then, acts of worship (Ibadah) are not limited merely to prescribed prayers or fasting. Imam al-Ghazzali in his book Arba'in has enumerated ten forms which worship can take:-
1. Prayers.
2. Prescribed Alms-giving.
3. Fasting.
4. Hajj or pilgrimage to Makkah.
5. Reciting the Holy Qur'an.
6. Remembrance of Allah in all possible situations.
7. Earning one's livelihood in accordance with the regulations of the Shariah.
8. Fulfilling one's obligations towards one's companions and neighbors.
9. Persuading people to act righteously and dissuading them from what is reprehensible and forbidden.
10. To follow the Sunnah, or the practice of the Holy Prophet (peace be upon him)
Therefore, not associating anyone with Allah in worship means that one should not love or fear or depend on anyone else as one loves , or fears or depends on Allah, nor should one repose one's hope in anyone else, nor should one consider obedience or submission or service to another as obligatory as the worship of Allah, nor make a votive offering or consecrate or dedicate anything to anyone or take a vow in the name of anyone similar to the way one does these things in the case of Allah, nor should one show complete self-abasement and total humility before anyone as one is required to do before Allah, nor should one engage in the particular God-oriented acts of worship for anyone other than Allah, acts which symbolize the farthest limits of self-abasement, such as, ruku and sajdah (the bowing and prostrating in salah).