The laying on of hands has multiple uses in the Bible. However, in a
general way, it almost always portrays the bestowing of something from
one to another. Jacob laid hands on Ephraim and Manasseh in order to
bestow a blessing them (Genesis 48:14). On the day of Atonement, Aaron
laid his hands on the live goat in order to put the transgressions of the
children of Israel "on the head of the goat" (Numbers 16:21). Moses laid
hands on Joshua in order to bestow upon him the authority for leading the
children of Israel (Numbers 27:22-23). Jesus often laid hands on people
when He healed them (Luke 4:40).
These are just a few examples of several dozen instances of the laying on
of hands in the Bible. You give some good examples in your question from
the book of Acts. The practice clearly gave weight to any time when some
sort of blessing or authority was being granted to another. However,
Jesus did not always lay hands on those He healed. As you point out, the
Holy Ghost did not have to wait for the laying on of hands in order to
fill or indwell believers (see also Acts 10:44-48). The laying on of
hands gave an external picture of the bestowing of any gift, but it was
not required for God to act.
I think it is good to include the laying on of hands in an ordination
service. Sometimes people lay hands on people in special cases of
sickness as they pray for them. This is certainly alright, though it is
not commanded for us today. We must understand that the laying on of
hands was symbolic. It does not make something happen and it has no
magical power. God can work with it or without it. However, it adds
gravity to a serious act and graphically shows the giving and receiving
of certain gifts.
