With airlines tightening up redemptions on premium classes and the huge devaluations that have happened over the last couple years more people will find themselves traveling in economy even though they may have originally been saving for business class redemptions.
This is where doing some homework can really pay off. Conde Naste has a good article on finding extra legroom seats. Even if you redeem miles, you can usually pay extra to have these seats when you choose your seats.
You should also check the exact plane configuration on Seat Guru and read the comments as some seats can have problems such as ife boxes under seats which reduce your legroom. You can also check the width to see how closely you will be crammed in next to your seatmates.
I personally prefer to fly on smaller planes which have 2 x 2 seats on opposite sides of the aisle so my husband and I don’t have to sit with a stranger, so I always choose these planes over a 737. We also prefer more seat width to more legroom so Seat Guru shows us what our options are.