How to check the postdoc opportunities in a specific lab even if there is no position-call from them? I'm about to start the last year of my PhD and apart from filling the gaps in my work i started to check the postdoc opportunities here and there.

The thing is that i found a few Labs (university groups) which are working in a more or less same area as i'm doing my PhD. Well, their not doing exactly same thing i do but still same category (Motion Analysis), and they are good at it! 

So i like to work with them as a post-doc after finishing my PhD. But i couldn't find any post-doc in their website. So how does it work? should i just sit down and pray to hear a post-doc call from them in the exact moment (ex. a couple of months before my PhD is done) :)  or is there another way to approach/contact them regarding this purpose? 

If is it the latter case, then how? should send them emails now directing asking about post-doc opportunities regarding 1 year from now?
Yes. This is how it works.
Once you find a lab, find a professor who you would like to work.
And then, 


Read his publications
Read them again to look for potential areas where you find yourself as a useful asset to that lab, like methods or instruments you are familiar with and used by the professor too.
Email the professor asking for available positions. Send in your email your CV and statement of purpose.
If you could add a document where you could be an essential asset by proposing additional ideas related to the professors published articles, it might add value if you don't sound arrogant.
While involving in such activities, if you find a wonderful result try to publish it and cite the professor's work on which you are trying to develop. This will make your application be outstanding and successful.


The right time to do so is when you are in the middle of the year before your last year of Ph.D. Also, you should let the professor know that you are writing him a year ahead so as to plan accordingly.