Each year, online dating Web sites attract more than 40 million Americans, many of them in their 40s, 50s and 60s. In fact, the fastest-growing segment of online daters is people over age 50.

But there are many pitfalls that can get in the way of a successful online dating experience.

How to avoid the most common mistakes…

FLAWED PROFILES

The profile and photos that you post on a dating site will determine whether potential partners take an interest in you.

Don’t focus on your life story. Focus instead on what you’re looking for in a partner and a relationship and what you enjoy doing. Be specific—for instance, don’t just say that you enjoy travel and reading. Give interesting examples of where you like to go and what you like to read.

Don’t write too much about yourself. Daters tend to think longer profiles lead to better matches. But longer profiles often are not read at all. Save the nitty-gritty for e-mail correspondence and dates.

Don’t rule out certain types of people in your profile. Doing so will make you seem judgmental and negative. Say what you are looking for…and then, later, you can politely turn down (or not respond to) people who don’t fit these criteria.

Example: One woman’s profile instructed men not to e-mail her if their divorces weren’t final or if they were experiencing financial problems. But these instructions sounded so judgmental that it turned off single, financially stable men, too.

Don’t assume that mentioning your children or grandchildren is a turnoff. It shows that you are family-oriented, something many potential partners in the over-50 age group find appealing.

Don’t include suggestive photos. Posting sexy, revealing photos might seem like a good way to attract a mate, but in my experience, it usually does more harm than good. Such photos are particularly likely to scare off people looking for a relationship, not just a fling. Select photos that make you seem warm, friendly and approachable, not hot and sultry.

Helpful: Include at least one photo that gives some indication of your overall body. Men in particular tend not to respond to potential mates if they cannot see a woman’s general shape.

Don’t include photos of yourself that also include members of the opposite sex. These tend to significantly reduce responses. They make you seem like someone who isn’t ready to settle down.

Don’t submit badly out-of-date photos. Potential partners will feel duped and disappointed if your current age, weight or hairline is very different from what your photos indicate.

FAULTY FOLLOW-UP

What not to do when you make contact with potential partners…

Don’t worry about “chemistry” too much when you exchange e-mails. It’s prudent to exchange a few e-mails with potential partners before meeting or chatting on the phone—just remember that some people don’t express themselves well in text. Agree to chat on the phone if the match seems feasible even if you don’t feel a spark from the e-mails. If the phone call is enjoyable, agree to meet in person even if that spark is still lacking—sometimes chemistry doesn’t appear until couples meet in person.

Example: Jane, 52, thought Mark, 67, was too old for her as they exchanged e-mails and chatted on the phone. But when she met him in person, she found him warm and handsome and much more youthful than she had imagined.

Don’t provide your home phone number and main e-mail. You don’t want to worry about angry calls or e-mails or, worse, stalking, if you decide not to pursue a relationship. Open an e-mail account and a Google Voice phone number (www.Google.com/voice) specifically for online dating.

Don’t assume that you’re in a relationship just because the e-mail exchange has gone well. Online daters often cultivate several potential relationships to see which turns out best. You might be disappointed if you get your hopes up too soon.

Don’t discuss prior marriages on a first date. Prior marriages often come up when people in their 40s or beyond date. But if this comes up on a first date, say, “I wouldn’t mind telling you about my marriage if we see each other again, but right now, I want to get to know you.” Discussing prior marriages on a first date can be a downer.

Don’t assume that online dating won’t work for you because you don’t express yourself well via e-mail. One of the latest trends in online dating is “meet-ups,” where dating-site members gather in person, typically in a bar. Match.com has been particularly active in arranging group events. It’s a great option for people who struggle to express themselves in print…and those who prefer low-stress informal gatherings to digging through online profiles and asking people out.

Group events tend to be quite friendly, and the dating sites that sponsor them strive to make them gender balanced and age appropriate. Because the people who attend are looking for partners, the odds of finding a match are a lot better than they normally would be when approaching strangers.

Helpful: RSVP immediately if you get an invitation to a meet-up and wish to attend—they tend to fill up fast.

DATING WEB SITES FOR EVERYONE

Dating sites can be divided into two categories—mainstream and niche.

Mainstream sites: These have the biggest memberships, providing more potential matches.

eHarmony is more of a “matrimonial” dating site—most members are hoping to find a future spouse or long-term partner, not just a fling. New members complete a detailed questionnaire, which eHarmony’s computers use to identify potential matches that it suggests to members. It has many members over age 40, making it a great choice for people in this demographic. ($59.95* per month…$179.70 for six months.) www.eHarmony.com

Helpful: Answer the optional additional questions on eHarmony’s questionnaire, not just those required.

Match.com has some members looking to marry and others seeking more casual relationships. Members usually search Match.com’s database on their own, although the company sends e-mails suggesting matches as well. ($39.95 per month…$119.94 for six months.) www.Match.com

Plenty of Fish is the largest free dating site and is easy to use, but some people complain that the lack of membership fees results in too many ads and unappealing members. (Although a basic account is free, an “upgraded” account that features increased profile visibility and other advantages costs $35.40 for three months…$51 for six months.) www.pof.com

Niche sites: These can be useful if you know the specific type of person you seek.

Alikewise is for book lovers. Users can seek potential partners who share their reading preferences. (Free.) www.Alikewise.com

Christian Mingle, whose slogan is “Find God’s Match for You,” includes questions on denomination and frequency of church attendance. It is the largest Christian dating site. ($29.99 per month…$83.94 for six months.) www.ChristianMingle.com

Date My Pet is for animal lovers. ($14.95 per month…$39.95 for six months. Free “basic” membership also is available, but it does not allow you to initiate online exchanges, only respond to them.) www.DateMyPet.com

Fitness Singles is for people who are active and in good shape. ($34.95 per month…$89.70 for six months.) www.Fitness-Singles.com

JDate is the largest of the Jewish dating sites, which also include SawYouAtSinai.com—a site focusing on more observant Jews. (JDate is $39.99 per month…$119.94 for six months.) www.JDate.com

OurTime is specifically for people over 50. ($19.99 per month…$71.94 for six months.) www.OurTime.com

Stache Passions is for men with facial hair and women who love them. (Free.) www.StachePassions.com

VeggieDate is for vegetarians. (Free two-week trial…$51 for six months.) www.VeggieDate.org

* Prices in this article are subject to change.