The rule of thumb is around 400-500 words. It allows you to get a decent keyword density within the article. Plus, reader's attention spans are not going to do well with a longer article. Try to keep it short and compact your information. Place your keywords about 75-100 words apart and you should do well. Cheers~
300-500 words best for an article.But important thing is that article is must be on valuable thoughts.Like altering advice is a very nice article.
nowaday i usually do 500 - 750 , so to put it good content and also take my time to detail the info for reader . look at it this way , the more you write the higher the chances you get keyword into your content , random keywords do take up 20 -30% of my traffic .