They are action words. They all require us to take action. They all require different actions. I believe seek has more intensity, because it requires us to seek God until we find him. We must always be asking, seeking and knocking in search or our Lord. Ask and you will receive, seek and you will find and knock and the door will be open. We must realize that these things will happen in Gods time not ours. For God has perfect timing. And he may answer in a way that is unexpected. But he always hears our petition. We must be persistent and ask, seek, knock daily,for this is what God wants us to do, to continually be connected to him in prayer.