I've been a graphic designer for nearly 20 years but over time I've had to do more and more marketing work. This has included the writing of press releases and magazine articles.
To boost my knowledge I went back to college and took a print journalism course which I'm happy to say I passed.
Anyway, I think the best advice I could give about effective writing is that when you do put a piece together, think of it in press release terms. By that I mean chose words that really 'sell' the point you are trying to make.
Don't use words like 'things', you must be more specific so it's clear what you mean. For example, if you were writing about what happened to you today you could say:
'It's been an OK day today. It was windy and cold but we still went to the park. We had a nice time.'
This could be rewritten as:
Despite the dreary, overcast weather with a wind that chilled me to the bone we still went for an amble in the park. We were well wrapped up in our snug jackets and woolly scarves and just had a great time kicking around in the leaves like kids. A day to treasure!'
The key is to chose words that describe the feelings you had. If it was windy how windy was it? Was it a draught or a hurricane. Paint me a word picture so I can feel what you felt. It's that that keeps the interest.
Oh, and a rule of thumb I was taught is that sentences should on average have around 22 words (and not the 68 that I was sent in an email the other day!)