I went back and read some of your older posts, and have been following this discussion. A couple observations and suggestions here:
- Take the spelling and grammar criticism to heart in all of your written and verbal conversations. It marks you as educated, mature and at least a little erudite. It's a good habit to have. Remember, you will be writing invoices and written reports to clients on what the problem was, what you did to fix it and what the final results were.
- Since you are still inexperienced, take stock of what level your skills are at, where your strengths an limitations lie. When you first start your business, concentrate on taking on smaller jobs that are within your skillset and politely decline invitations for work that is beyond you. As your knowledge, skills and experience grow over time, you'll be able to take on more complex jobs.
- You have a lot of things going for you - enthusiasm and a desire to work in a field you like not the least of them. Even though you are young now, the calendar marches on whether you like it or not. To counter what you think might be a negative perception based on your current youth, concentrate on things you can do to appear older than you are. As an example, wearing a nice pair of slacks, shirt and tie always helps. Take a look in a full-length mirror and try to imagine how your clients see you.
- Give each job 110%. Go the extra mile. Keep your customer involved and informed as to what you are doing and try really, really hard to explain things to them in the King's English using terms and analogies they can understand and avoid "Geek Speak" as much as you can.
- When you arrive at a client's location, introduce yourself, shake hands and offer two of your business cards. Why two? One for the client to keep and another for a spare and hopefully maybe pass on to someone else as a recommendation.
- Arrive at the client as prepared as you can be. When the client first calls you and you're first discussing the client's complaint and arranging the appointment, get as much information as you can about the client's system. Then, before you go, familiarize yourself with that system, do a google search on what you know about the client's problem, maybe download some drivers and put them on a USB stick to bring with you. Bring your basic tools and bag of tricks.
- Always show up on time for your appointments, where "on time" is defined as five minutes early.
Best of luck to you and... keep in touch. Lots of help, advice and resources here. Take advantage of them, but don't abuse them... I think you know what I mean.