when I find myself struggling to play something I always break it down in more managable parts.
Let's take the B for exemple. I would start by concentrating on the index finger to make sure every string sounds correctly.
The first exercise I would do is to alternate from the open strings to the barred index position.
Exercise
--0--2--0--2--
--0--2--0--2--
--0--2--0--2--
--0--2--0--2--
--0--2--0--2--
--------------
Once I can make the switch easily, I would concentrate on adding ONE finger.
--0--2--2--0--2--2--
--0--2--2--0--2--2--
--0--2--2--0--2--2--
--0--2--4--0--2--4--
--0--2--2--0--2--2--
--------------------
And move on like that until I get the full chord correctly. Once I can switch to the open strings to the barred index and to the full chord, I would drop the second step (barred index finger) and just practice switching from open strings to playing the full B chord.
This is a very long approach to learning but I assure you the chord will stick forever in you mind and you'll be able to recall it whenever you want
I suggest you look at Lisa's tutorial on switching between chords, this will probably be your next challenge.
http://guitartricks.com/tutorial.php?input=484
http://guitartricks.com/tutorial.php?input=463
If you want to learn more on my approach of breaking down exercises to learn them, I made a tutorial showing how I do it. It's aimed at lead guitar but the principle can be applied to anything else.
http://guitartricks.com/tutorial.php?input=498
I hope this helps you out.
Let us know if you need more help.