How can we find comment sites or blog for Do-Follow backlinks? can anyone suggest any trick list?

commented: As you claim to be a web developer, this is not good for your profile or attracting business. -3

I would have thought that a web development outfit such as yours would already know the SEO basics such as this...

You need to find the top litas of popular sites and blogs in your niche. I recommend referring to your competitors' backlinks. You should place your links in the same place where their links are located.