I just got to Alltrades Abby and was really excited to be able to choose a new class.  I'm new to the DQ series and my last true JRPG game was probably FFX so forgive me if I don't really know how this works. 
 
When you choose a new class you drop back down to level one, with crappy HP/MP and your spells all gone.  So what is the point?  I know you can change back to your minstrel character at any time, but I just don't understand why you would trade at all.  Do stats carry over?  Skill points?  Why should I bother? 
 
Please, if someone could give a DQ noob a tip or two, I'd appreciate it...

Well I am not up to that point yet. This game reminds me of DW3, in that game you where the hero class, and everyone else could be one of a lot of other classes. The idea is yes you can change classes, but when you do, you do go back to level 1, however you kept half your stats so a warrior with 800 hit points and tons of strength could come back as a pretty bad arsed over 400 hit point having level one mage (and yes he would have half that strength and usually start off with bonus MP due to the higher intelligence stat from the previous char being a high level).
 
I really hope this one let's you carry over your skills you master as time goes on along with advanced classes. In DW3
 

Juan summed it up quite nice: you become a stronger level 1 with the ability to relearn the spells you had before. As such, you can go into areas that would normally decimate level 1's and grind back up rather quickly into something more powerful and more flexible. I used to love doing this with priest-to-mage and vice versa combos as it would mean I'd have a main healer that could also do some decent nuking, and a nuker that could do some decent healing in DQ3.

I decided to come back and clear some things up.
 
So in this game stats are reset to that of a level 1 character. If your class can not learn spells on it's own, it will not be allowed to carry them over from a previous classes levels. What you do get to carry over are skills learned through the skill point system, as an example, if your character knows dragon slash and changes to a wizard, he will still know dragon slash. I believe this covers all stat boost's as well gained through the skill point system, so that is kinda your "start with half stats" I mentioned. the big thing is you can equip all the weapons available to that class with no level restrictions, so your level one character can easily have a bad ass attack and defense......but low hit points, but than again the enemy is not hitting for much at that point lol.
 
Any skill points put towards a weapon skill set carry over from character to character and your allowed to build on them. In this respect my best advise is to seriously consider maxing out every characters core class for their class specific skill set. It would really stink to say be 10 points away from getting omnivocational (probably meaning spells carry over from class to class and your allowed to use all the equipment of said class) in a class and missing it because you maxed out your level......this is assuming the maximum level is some such as 60-80-99-or 100. If there is no max, who cares than?
 
All I know is I will be a bit ticked off if I am scouring the land for skill seeds to raise my mains minstrel skills because I focused on making him the ""tank" by slamming sword skills for extra damage. 
 
This game is seriously frustrating at times in the respect I mentioned above happens a lot and since nothing is explained I could have already screwed the pooch as they say. Oh well I am going back to making everyone who is not a thief, a thief, until they all learn to steal, and than back to their original classes. Having one char steal all the time and fail is a pita and wasted several hours of my time so far trying to get specific alchemy ingredients.
 
Now if I could only figure out if all the time I spend on this game is a form of OCD or because I am actually enjoying it. All I know is I am not bored really, because time flies and does not drag when I play.