It seems these days, that more is more when it comes to wedding design. Instead of a guest book, have a Polaroid station with glue sticks, scrapbook, markers, and tape. Instead of a plate, how about 4 stacked atop each other, with a floral treatment? Why stop at a few votives when you can mix in tall hurricanes and tapered candlesticks as well?
Adding "more" in these situations isn't necessarily a bad thing, but it's good to know when to stop.
Don't overstuff your tablescape.
Too much stuff on the table has become a trend - from lots of candles, multiple pieces of glassware, placemats, lots of dishes stacked up. People can't even rest their forearms at their placesetting if there are too many items! Consider the size of the table, rent larger tables if necessary, and treat it like putting together an outfit: the rule of thumb is, look at yourself in the mirror and remove one piece of jewelry so you don't overdo it. Same thing with wedding design - if you've got tons of candles, lots of plates, 3 glasses...remove a glass, trim a few candles, and cut it down a bit. Consolidate - perhaps use table numbers that can fit inside the centerpiece, for example.
Consider the elements.
If your ceremony space is windy, you want a really stable arch versus centerpieces precariously placed on pedestals. If your reception space is outside, escort and seating cards will probably blow away; consider a framed seating chart or tuck name cards in a folded napkin.
No more favors!
This blog post from the awesome site the Budget Savvy Bride features some great planners and event pros that say, 'nix favors'! They're often unpractical, or hard to travel with (I've seen many a mini succulent left behind). Technically there is 100% no need to offer favors at your event, so no need to consider them when planning your wedding design - so don't bother unless it's something you're really passionate about.