Well, from the jobs that I've done (My Sim, Sammy Stratssand, reached level 10) there's a few things that I find massively help decrease the number of bad reports in the Architectural Design Profession. Here are the ones I go by on every job.
1. Don't edit the houses walls! Sims seem to hate this and say something like "I can't believe you did that to my house!" or "I'm almost embarrassed to invite people round now!". Although, if you are thinking of trying to get to the top of the AD profession sometimes editing the house will help in the long run. Once I got asked to do a Gym Studio, and I created a new room on the bottom floor. I got a bad report. Then, later, I got a request in from the same family and I used the old bad report room as the new bedroom, and I got a good report.
2. Don't "Clutter" things! This means that everything has to be accessible. I've had this a few times, but I haven't ever had a bad report and this complaint (You've cluttered things a bit. How am I use to get to my new stuff if I can't get to it?" or something like that)
3. Try to use your own sculptures or paintings as often as possible. In your Sims spare time after work hours make them (using a AD table (fastest, I find), forgotten the name!) paint/sketch. I find is best, as you can get about 4/6 done in a week (depends, really. Mood and skill change the amount + babies and toddlers) and if you remember, putting a even a small painting in makes people happy. I just put in the ones I don't like.
4. The list the client gives you is not just what you can get! Normally, I make a rug that is designed for the room or client. Put in plants and cheap decorations and normally the score is raised.
I hope this helped. I haven't read the guide on the website, but hay, I'm sure you don't mind.
Thanks for reading.