It's hard and may not be the best use of your time. As an agent, you must put their needs ahead of your own. If your market is improving as it is in many areas, time "may" be on the seller's side. If they are also a buyer though, it may work against them as more expensive homes go up in value and the affordability gap becomes greater.
Don't focus on one potential client or become more motivated than they are. You will be pulling them against their will throughout the whole transaction. Keep your client informed as to what the market for their home is doing and for what the market for their next home would be too and focus on finding other buyer's and seller's who are ready now.