Calling from the blinds

[deception5]

Hi all,

A situation which comes up fairly frequently is when someone open raises in middle-late position, gets 1 or more cold callers and I'm in the big blind with a marginal hand, but getting great pot odds. Likewise when there are a few limpers and I'm in the small blind. I'm trying to figure out when I should be throwing these away and when I should call. Is there an easy way to figure out (or rules of thumb) about what hands would show a profit in this situation? Here are some examples:

1.) I'm BB, MP1 raises, MP2 calls, Button calls, SB calls (so I'm getting 9:1).

I have:
a.) J5s
b.) 98o
c.) 72s
d.) 54o

2.) I'm BB, MP2 raises, SB calls (so I'm getting 5:1).

a.) 98o
b.) 54o
c.) 34s
d.) K7o

3.) I'm SB, MP2 limps, CO limps, Button limps (so I'm getting 9:1).

a.) 98o
b.) 34s
c.) K7o
d.) 72s

Thanks for your help!
D5