There's much to say on this topic, and let me begin by saying that I am no expert... however, I will share what I've learned along the way.
A lot can be said with your emails, avatar photos, profile pictures, attitude, and even (gasp!) grammar and spelling.
With emails - it starts with the address. Moreover, you'll be taken more seriously, in my experience, if your email is something simple like your name, "firstname.lastname@example.org" rather than something sounding like a gamer profile, "email@example.com" or "rainbowzRpurdy@email.com". One of the first lessons of the internet for me (at what now seems like the beginning of time) was to change my email address to reflect my professional self, rather than my silly alter ego.
(incidentally, my very first email address was blookie_nose (at) hotmail (dot) com)
Another thing to keep in mind is your display name (for when emails arrive in someone else's inbox). Several years ago, I was busy sending out emails regarding job openings and applications. I applied to several jobs that I felt I was highly qualified for, and for some reason, got no response. I called a few and left voice messages for the employers, but ultimately nothing came from it. Why?
Weeks later, I received a returned email and saw a possible reason why nobody had taken me seriously. A million years ago when I set up my email account, I set it to say "Shanananoononon" or something like that. No wonder those echelons weren't interested! Little tip: use your actual name, and make sure it's spelled correctly.
Avatar photos and profile pictures! Ahh! In a world of social networks, I think it's important, even when you think your profile is "unsearchable" to maintain an air of professionalism. Nowadays, more often than not, employers search for you on Facebook and MySpace before really considering you for employment. Make sure that whatever they find can't be misunderstood. Meaning: don't post your drunken/naked/illegal activity photos on your social networking profiles. If you don't want someone to find out about it, don't post it. I like to remind myself of something my acting director told us during dress rehearsal. She said, "Remember. Someone's always watching." and it's true.
Extending beyond social networking sites - are the instant messengers like Skype. I recently had a minor freak-out when I got a chat invite from the actual software developer of a program. He was wanting to get in touch about a specific issue I was having - and as soon as I received his request to chat, I noticed my avatar. A zombie photo of myself from Halloween two years ago!
I was slightly embarrassed, to say the least, and quickly changed it to something more appropriate (a simple headshot of myself).
Attitude is a biggie. Clients and employers alike can be turned away by the way they are treated. When I worked at a call center for a major credit card company (I'm sorry!!!) we were instructed never to interrupt and never to raise our voices to the person on the other end of the phone. That rule seems so simple - but for me, someone who likes to argue when I know I'm right, it was very difficult. It was also one of the best lessons to learn. People are often surprised when you don't interrupt, and just take the time to listen to their concerns. The main goal now is to carry that over into my personal life. I'm sure my husband would appreciate it... :)
Make sure not to spread yourself too thin. This is something I've learned the hard way a few times too. I learned not to try to make everyone like me. Just take on a few clients at a time and make sure they're well taken care of.
With employers, well, every employer is different but I suppose the main thing is just be polite. Always be polite, no matter what situation you find yourself in. That in and of itself is something that will leave a lasting (and positive) impression, even if things end poorly.
Spelling and grammar, unfortunately seem less and less important these days. Again, I'm no expert - but I do put my best foot forward when it comes to these things. I often see simple words like "tomorrow" or "definitely" spelled incorrectly, not to mention the misuse of "your" vs. "you're" or "there", "their", and "they're". Another common one is "its" vs. "it's". These words are thrown around billboards, movie posters, and ads with not a care for whether or not it's correct.
That being said, it doesn't mean I shouldn't know them when writing a cover letter or professional email to a client. Set yourself apart with your good grammar and spelling, and you never know the possibilities.
(via: The Oatmeal)
That's pretty much it, I think. All these things are lessons I've learned the hard way at some point or another, and I hope you may find some of it useful!