I hope someone can help me, I am trying to figure out which MOSFET to use with a 12V solenoid which draws a current of 8amps (it is a v big solenoid). I am a newbie to a lot of this stuff so apologies if this is super obvious. Thanks in advance.
Have had good results from these.
Check the amperage at the Vgs used.
Correct. You need a logic level N channel MOSFET switching the low side of the load. And of course one managing some 15-20 Amps (to have margins, no problem to find). Do use a kick back diode across the coil.
Thank you. Yes I will use a diode to stop the kick back. I guess I was just unsure which exact MOSFET to go for as I am slightly confused by a lot of the terminology, but I am researching 
. And logic level would be good as I am using arduino.
If your solenoid draws 8A, your diode will need to be ~10A.
There are 4 or 5 MOSFETs in the PDF offered you, over 10A and are logic level.
Amazing, yes I have just found a few. Thanks for pointing me in the right direction.
Good!
Too many members miss that and face unexpected resets, hangings etc.
When looking for components, DigiKey.com and Mouser.com are good sources. They provide "parametric search". You start with a search for the kind of device you want: MOSFET.
That will list categories that contain that keyword. The first one is "Transistors - FETs, MOSFETs - Single" which sounds right so select it. That lists 42,308 devices. Then you start paring down parameters. Select "Product Status: active" and "FET type: N-Channel" to narrow down to 18,308. If you want it soon, check the "In Stock" checkbox to narrow it down to 5,888 devices. Now you can select your Drain-Source voltage. The options left (active, in-stock, N-Channel) are 8V, 10V, 12V, 15V, 20V, 24V, 25V... Of those, I would pick 15, 20, 24, and 25 (above your minimum and not massive overkill). That gets you down to 346 devices. To get Logic Level devices select anything with "Drive Voltage (Max Rds On, Min Rds On)" that has 5V or lower for Min Rds On. That means it turns fully ON (minimum resistance) with a Gate-Source voltage of 5V (logic level). That gets you down to 210 devices. Are you OK with soldering surface-mount devices? If so, the prices start at $0.25 each in single quantities.
If you need a through-hole package, your choices are mostly massive overkill: 60V 17A but only about $2 each and will do the job.