Pirating/Boarding - WORK IN PROGRESS!
Pirating in X:R can be broken down into two interconnected groups: looting & boarding
Traditional pirates (c15-c18) had two goals: first to make money (to keep their crew happy); second to gain better ship(s) that they could then sell off as 'prizes' or use to increase their fleet strength. In X:R we can currently ignore crew morale, so it's up to <player> to prioritise cash, cargo or hulls as they see fit..
So, WHY do you want to pirate other ships? Do not dismiss this question!
Do you need their ships (hulls)? If so, what will you do with them? Sell them for cash or put them to use in your own fleet?
Do you need their rare and/or expensive cargo?
Has a certain faction upset you so much (or you've upset them) that you want to get back at them (revenge)?
Are you a collector who wants one of every ship available to own, or are you a badass who just likes pirating no matter the consequences?
The above statements will (hopefully) clarify your thoughts on how to go about pirating.
Hacking:
Internal: If <target> is non-hostile you can dock. Enter the 'shed' (the small covered structure directly in front of you, often containing lockers) & at the back, to the right, there is a shield control panel available for you to hack using the craftable Security thingy. If you successfully hack this the ship's shields will be disabled for a time (all the main shields plus most of the turret's shields on a warship). There's a similar panel elsewhere to disable turrets, I think.. but you probaby won't want to hack the Repair panel in the 'shed'! Shield hacking will significantly reduce the time required to board <target> if that's your objective, as you can immediately start reducing hull strength when you're ready rather than fighting your way through shields first..
External: The Trojan (hacker) drone can disable shields, engines or turrets, or cause the ship to drop cargo depending upon which hack points you successfully complete. If used /prior/ to Yisha's boarding demands it will take 4 or 5 successes to hack <target> (Yisha only requires 1 success per demand). I find the minigame difficult & irritating so I don't generally bother, but others may have more success here..
If you want the hulls for your own use
You'll want to intercept <target> & destroy their engines/Jump as quickly as possible while out of range of any hostile stations or patrol ships. The TO DLC adds a 'Constrictor missile' (only available from TO sectors' Arms Dealers) which disables boost for a time when (if) it hits.. Full operational details for this missile are not currently available. Another method is to mine the engines with the Traitor drone, then remote-explode the mines when the ship moves to a convenient spot*..
*I'm unsure of the range of remote-detonation. IZ certainly, but it may extend beyond that with the reworking of game range mechanics as described elsewhere..
A Rahanas freighter is an easy boarding target on paper only. Its hull is so weak that a slight miscalculation or stray shot may destroy the ship with your marines onboard, & it has so few defences that its main asset (its drones) are at great risk of being lost to Yisha's boarding demands (destroy Drone Bay). If possible choose a Sanahar over a Rahanas: the hull is stronger, defences are better & (slightly) more numerous & its speed & maneuverability is much improved over the earlier model
If you want the cargo
You can hack <target> using the Trojan drone, or board them. If you hack them be aware that ejected cargo containers have a 'lifetime'; if your pickup drones don't get there in time the looted containers will self-destruct.. so make sure you have a suitable cargo ship nearby before you start this procedure!
If you want the cash
CHECK FIRST using your scanner & target information system to see if there's a market for the ware(s) <target> is carrying! If the wares are unsalable (currently eg (v4.00b2) Plasma Jets & Hailstorm) then a lot of profit is lost immediately. HOWEVER you can still sell the ship with its cargo to a convenient shipyard to recoup at least some of the cargo's value*
If you've boarded <target>, as always transfer a 5* engineer to it ASAP. Not only will this improve its speed as its engines are repaired, but it'll repair the hull & turrets too (quicker if you're OOZ). A fully repaired hull sells for a fair bit more than an immediate capture, & you can recall the engineer (& captain if you've given it one) before selling the ship if necessary
*Probably its average value as defined in the Encyclopaedia, but there may be a discount; I haven't checked
Collector/Badass
Pick up tips from the above, then go ahead & do what you want; you won't listen to me anyway 
I'll add to this later.. I'm going to bed now