Most all my climbs are seated. Standing is just for when I run out of a lower gear and can't keep my cadence up. Essentially it's a last ditch effort to keep from walking the bike over the hill. I should practice it more though because standing really uses different muscles or at least it uses them differently.

I've always liked my saddles further forward and am willing to carry weight on my arms. So if your seat post has a lot of setback, then maybe look for a zero setback post. Having my saddle closer to the BB's vertical centerline is what I feel helps me put more power into the pedals while climbing. And of course the saddle needs to be what is considered the proper height for a road bike. If you like your saddles low, then you'll be wasting some energy because of the angle between your pelvis and upper leg as well as the angle between your upper and lower leg, IMO.

A high cadence also helps for climbing seated. For short climbs I want to get up quickly, I'm 90 rpm or better. For just cruising I'm in the mid to low 80's. And I don't have what I'd call strong leg muscles, so I use a gear combo that doesn't take a lot of muscle. That way I don't burn out my legs before I get to the top.