A friend gave me a pair of meadowlark kestrels hotrods. There are 4 post on back of the speakers, 2 for tweeters, 2 for bass woofers. How is bi-wiring done? I have them piggybacked from +tweeter to +bass, -tweeter to -bass. Any harm in wiring them like this? If so, how exactly does one bi-wire? Thanks in advance!
You either use one run of speaker cables from the amp and then add jumpers such as

Or two identical runs of cables from the amp

some people even bi-amp, one amp and cable for each binding post on the speaker. 

Never tried the latter but I will say I prefer the sound of bi-wiring to single cable with jumper.

Bi-wiring works best with lamp cord or really cheap wire. The improvement/cost ratio is pretty good then. Technically its not that good even then, it just feels like a better deal when its only $2 more than when its $200 or $2000 even though in every case its twice as much. As you can probably tell just by the numbers when you start getting into the better more expensive cables it quickly becomes first harder then impossible to get as much improvement from two as you could get by putting the same money into one better cable. 

Don't take my word for it though. Try bi-wire now while its cheap. Then try some really good speaker cables. I doubt you will ever want to go back to the lamp cord.

Best to get the rest of your system straight before worrying about biwiring. One thing I will say is that until you can justify spending money on doubling up on cables, you can get a good benefit from replacing stock jumper plates with some short runs of decent cables to bridge the terminals. I shotgun biwire my speakers and in my situation there is a benefit, but upstream electronics improvements were more impactful on an absolute basis.  Frankly, I'd even get my interconnects and power cords set before addressing the biwire issue.  Just my experience in my system FWIW. 
I got a pair of Kimber 8PR very cheap.  Spades on the amp side and bare on the speaker side.  Separated the black and brown wires into a 3/5 configuration 3-tweeter, 5 for the woofer on my Ref 3A de Capos.  Does it sound better who knows but it does sound good and i got to 15ft runs with WBT spades for 120.00
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you have a wonderful friend !,,,

great speakers, like most made better by biwiring

you can read about the theory, application etc or just listen.

for best effect get the treble wires 4” away from the bass. This is called an external biwire.

have fun

enjoy the music

Thank you all for your responses. Another question, though- how would bi-wiring look on the amp side?
Yogiboy, thanks! Exactly what I was looking for!
My bi-wiring with used good cable was a success... With a costly cables it is not worth the subtle upgrading effect... But with good used cable at low cost it is very interesting little upgrade...
Bi-wiring utterly depends on the speaker as some benefit from it and others don't. Example: I had a pair of the excellent Silverline Preludes for years and when I spoke to the designer (thought I might need a woofer...I didn't), Alan Yun, he told me that although other models in his lineup should be bi-wired, the Preludes sounded better single wired. I tried both, and he was absolutely right...more coherent (his words).