The Benefits - Well first, the benefits. There are 2 clear benefits from leaving comments:
1. If the website you leave the comments on goes along with the dofollow theory, then you are very slightly helping the search engine optimisation of your website.
2. If your comment is useful then several readers are bound to take an interest and want to find out further around you and will click your link back to your web site. This is the big bonus!
Do not worry round nofollow / dofollow if you don't understand it. But in short, many blogs prevent the search engine benefits to reduce spammers hitting their web site and in fear it will leak their own Page Rank. The main benefit is the traffic that the comments will produce.
Successful Visitors - So, what steps do you need to take to successfully gain a trickle of visitors through commenting?
Well, for a start, you need to find several blogs that will be of interest for your customers. Preferably some with stacks of readers. But, if you can find them so can your customers.
Add Value - Next, read a few posts and comment on only one post. But forget the "Nice post, I really enjoy your writing" type of spam comment. These are prospective to be deleted by the weblog owner and it is not nice-looking to the readers.
Your comment needs to add something to the post. If, for instance, the post is talking around a fish keeping problem and you have experienced it, then a mention what you did. Other readers might be interested in the fact that you cured the problem and then want to read additional around what you did.
Don't Get Greedy - This leads to the second point. When you leave the comment do not give any website addresses in the actual comment text. You risk being deleted as spam before you even start by doing that. Merely write a bit round your experience. Along with the comment you might leave your site address. This might point to your home page, or if you have a additional relevant page, link to it there.
Use Your Name - Next you leave your name. Numerous people try to spam the comments by not leaving a name but by entering their favoured keywords. Another fabulous way to have the comment deleted as spam. Leave your real name so that people see you as real.
Return For New Posts - And that, in short, is all that is required. Add the site to your RSS feed and watch for new posts and probably comment on them as well. Watch your site visitors stats and see where visitors are arriving from and then you will know which websites to keep commenting on.
Get An Avatar - Merely one last hint for this. Not an essential, but extraordinary to do. Go to gravatar.com and sign up to their service and load a suitable Avatar. This could be a picture of you or a company logo. It doesn't matter. But it means that on most web sites where you place a comment this image will be what readers see. This has two benefits.
First, the weblog owner sees your face / logo and is more associated with you as a real person.
Second, if readers are visiting numerous posts where you have commented they will see your picture several times and this will build up trust and they are then more possible to use the link.