Using an all-caps tweet is tantamount to shouting, and you obviously do not want to be seen as someone using SHOUTY CAPITALS, right?
Percentages work better than dollar amounts
More people click when they see percentages than those with cash discounts.
Don't go overboard on hashtags
I've mentioned before that 1-2 hashtags per tweet generates engagements, but as users evolve so is hashtag use in which you could try exploring eliminating hashtags at all.
Website cards basically summarises your website information and adds a thumbnail to your tweet, thereby creating a more professional-looking tweet as well giving your audience a quick summary of what they're about to click.