Today a site is offering .org and .info domain for just about $2 for 1st year only..

I have a doubt : if after one year, another company is offering domain cheaper then it, can i buy the same domain from that company or i have to remain stuck with the previous company..

Does the previous company get the hold of that name Or it expires after one year so that i can register the same domain with new company who is offering cheap domain names (after one year).

Also any idea how to choose a domain name.. like domain name suggestion tool. which is the best one?

Read the fine prints from domain registrars. It would be further helpful if you can provide the link to the domain registrar's website. Otherwise it's all hearsay.

But in the past, Tucows, Godaddy, 1and1 and other "cheap" domain name registrars have acquired expired domain names and parked to their own nameserver. This was one way to resell the domain name with higher price since it "could" be in higher demand.

The site netdomainindia.com with TLD .info and .org domain for about Rs. 79 and 99 respectively.. They dont sell expired domain, its our choice for domain selection if available..
Bu the offer is only for an year.

You misunderstood my answer to your second question Yes they will hold your domain if your domain expires and you fail to renew in time.

The answer to your first question is to purchase from another registrar before your domain expires with the option of "domain transfer." However, only few large domain registrars will allow this to happen. Again, read the fine prints and see if netdomainindia.com allows your purchased domain name to be transferred. 1and1.com and Tucows will not let you transfer to another registrar easily. Therefore, my guess is that netdomainindia.com may not.

Check out ComputingHost Domain purchases for inexpensive .org and .info names. ComputingHost is part of Xisto Corporation, just like Trap17.