Bhagavad Gita Verse 22, Chapter 11

rudraaditya vasavo ye cha saadhyaa vishveshvinau marutashchoshmapaascha |
gandharvayakshaasurasiddhasanghaa veekshante tvaam vismitaashchaiva sarve || 22 ||
 
The hosts of Rudraas and Adityaas, the Vasus, the Saadhyaas, the Vishwadevaas, the Ashwini Kumaaraas, the Maruts, the Ushmapaas, the Gandharvas, the Yakshas, the Asuras and the Siddhas, all of them are amazed, observing you.
 
rudraaditya : the Rudraas and Adityaas
vasavaha : the Vasus
ye : those
cha : and
saadhyaa : the Saadhyaas
vishve : the Vishwadevaas
ashvinau : the Ashwini Kumaraas
marutaha : the Maruts
cha : and
ushmapaahaa : the Ushmapaas
cha : and
gandharva : the Gandharvas
yaksha : the Yakshas
asura : the Asuras
siddha : the Siddhas
sanghaa : hosts of
veekshante : are observing
tvaam : you
vismitaahaa : amazed
cha : and
eva : only
sarve : all
 
Previously, Arjuna had heard about Ishvara manifesting as deities in the universe. Now, in the cosmic form, he is able to see them clearly enough to recognize who they are. For most people during Arjuna's time, deities were worshipped but were inaccessible, they were invisible. Arjuna was clearly delighted to see those deities that were only invoked and worshipped in rituals. Even though these deities may have had meaning to Arjuna, they may not have meaning to many of us. So let's look more closely at these deities from our standpoint.
 
We may not worship the Vedic and Puraanic deities mentioned in this shloka, but we do worship material deities. If we want a telephone connection, we approach the telephone company. If we want an internet connection, we approach the internet service provider. If we want to admit a child into school, we approach the principal of that school. Broadly speaking, when we want to access something that is beyond our reach, we approach a deity and convince them to give us access to what we desire.
 
In all these cases, there are three aspects - the individual, the object of desire, and the deity that connects the individual to the object of desire. In many ancient texts, it is said that the universe split into 3 parts during the process of creation. The individual is known as the "adhyaatma", the world of objects known as the "adhibhoota" and the presiding deity that connects the two, the "adhidaiva".
 
It is said that we should worship a deity if we are seeking to acquire certain traits. If one wants to acquire strength and power, he should appease that adhidaiva who presides over a storehouse of strength. So we see that seekers of power worship Lord Hanumaan. Seekers of dispassion worship Lord Shiva. Seekers of knowledge worship Sarasvati and so on.
 
So when we begin practicing meditation, we can choose a deity that we have a particular attraction to. Some people love to worship Shri Krishna in his childhood for, whereas some people worship Lord Shiva in his serene form. It does not matter which deity we choose as long as we use the deity to ultimately take our meditation all the way up to Ishvara.