This thread, among others, may answer some of the Qs of the OP:
http://www.puritanboard.com/f122/baptismal-mode-pre-christian-era-judaism-early-christian-era-56220/
A number of times in the NT John's baptism is contrasted with and distinguished from prior established ceremonial ablutions by being called "a baptism of repentance unto the remission of sins", which is what is also involved in Christian baptism. Christian baptism in the name of the Triunity is a "baptism of repentance unto the remission of sins" because one of the things it symbolises is the washing away of sin at which point there is also true repentance.
Little can be derived from the mode of Jewish ceremonial ablutions
(a) Because there is a Q if they were doing it as commanded by God.
(b) In their misplaced zeal the Rabbis focussed on the external and maybe were concerned that every part of the unclean person's body be touched by water.
(c) In the mikveh (baptismal pools) the Jews used, we do not know if they bathed in the normal way people bathe, sitting or stand in the bath and applying water to themselves or if they underwent immersion. And if they did undergo immersion was it necessary according to God's law, or was it a superstitious rite to make sure every part was touched by water?
(d) The Presbyterian position is that immersion is unnecessary and that people were baptised sitting or standing in water with water poured or sprinkled over them, or sometimes were baptised while sitting or standing in a dry place with water sprinkled or poured over them. Jewish and Christian immersion grew out of misplaced superstition, baptismal regeneration theories, and a misinterpretation of Romans 6:4. I.e. because we are buried with Christ in baptism we should be buried in water at water baptism. But how can we be e.g. planted (as on the Cross) in water (verse 5)? We are spiritually baptised into everything that Christ has done for us, and that baptism is symbolised in water baptism, but everything that Christ has done for us is not and cannot be symbolised by water baptism.
Here are some articles on ritual washings by Jews, some of which involve far more than immersion. Bear in mind that what Jews do, or did in the past, isn't necessarily biblical and sometimes involved unbiblical and superstitious, and sometimes frankly rather weird, additions.
Niddah - Wikipedia, the free encyclopedia
Ritual washing in Judaism - Wikipedia, the free encyclopedia
Conversion to Judaism - Wikipedia, the free encyclopedia
Mikveh - Wikipedia, the free encyclopedia