Do Hindus worship Idols or Statues?

Hindus do not worship an idol; they worship God through an idol. An idol worshiper is one who considers an idol to be God, as though God is nowhere else but in the idol. Hindus believe that God is everywhere; therefore they are not idol worshippers. In temple worship God's presence is invoked in a statue during the time of the worship (Puja). This is meant to help the human mind that needs to focus on a name and form for support.

What is the meaning of the symbol Aum?

This is a symbol of the supreme God. It is considered to be the most powerful word symbol for use in prayers and meditation.
Sound is the subtlest of the all idols and of all sounds AUM is most potent and the most natural. Hindus believe that it was the first sound produced at the creation of the Universe, the Big Bang. As such, everything emanates from this and represents the initial creation. The sacred word AUM is the name of God. It is uttered in beginning and the end of most Hindu prayers. It is considered to be the essence of Hindu scriptures and also represents the concept of one God.
The proper way of writing Om (monosyllabic) is AUM (three syllables). The latter symbolises the Trinity representing the three functions of God which are Generation, Preservation and Destruction.
'A' is the sound emanating from the base of the throat ; 'U' is produced by the impulse rolling forward in the mouth; 'M' is produced by closing the lips ---- there is no sound beyond these two extremes. So 'AUM' covers the full range of sounds and entire phenomenon of sound.

What is the symbol Swastika?

Swastika is a symbol of auspiciousness. It represents the world-wheel (life-cycle) or the eternally changing world around the fixed, unchanging centre or God. The fragmentation that occured at the Big Bang scattering energy in all directions appears like the figure of Swastika. It creates an impression of perpetual mothing and symbolises welfare. The angled arms of this ancient sun sign denote the indirect way that divinity is apprehended.
The Swastika of Hinduism is a religious symbol of auspiciousness, world peace and prosperity; it should not be confused with the Nazi swastika which has different design and a totally different meaning.

On entering the temple after removing one's shoes one rings the bell. This signifies to the pilgrim that he is entering the place of God and should therefore become alert and be conscious of Him. It also represents sound which is carried through the air. Air is one of the five basic elements comprising the universe and all existence.

Why do we use the Conch shell in temples?

A conch (Shankha) is in the form of multiple spirals evolving from one point into ever-increasing spheres. It thus symbolising the origin of the Universe from a single source. Being found in the water, it also symbolise the waters from which the Universe evolved and into which everything is dissolved. A conch shell is kept in temples and places of worship and is blown at times of special prayers like the Aarti.

Why is the Coconut used in temples and other ceremonies?

The coconut is an independent object of worship. A coconut (Sriphal - the fruit of God), is also used to symbolise 'God' while worshipping any deity. The three eyes of the coconut represent the three eyes of Lord Shiva.
One of the most common offerings in a temple is a coconut. It is also offered at occasions like weddings, festivals, the first use of a new vehicle, new bridge, new house etc. It is offered in the sacrificial fire whilst performing havan. The coconut is broken and placed before the Lord. It is later distributed as prashaad.
The fibre covering of the dried coconut is removed except for a tuft on the top. The marks on the coconut make it look like the head of a human being. The coconut is broken, symbolising the breaking of the ego. The juice within, representing the inner tendencies is offered along with the white kernel - the mind, to the Lord.
The coconut tree also symbolises selfless service. Every part of the tree - the trunk, leaves, fruit, coif etc. is used in innumerable ways like thatches, mats, cooking tasty dishes, oil, soap etc. It takes in salty water from the earth and converts it into sweet nutritive water that is especially beneficial to sick people. It is used in the preparation of many ayurvedic medicines and in other alternative medicinal systems.