I do research as I'm going along - so for example if I'm writing about someone who steals a boat - I know next to nothing about boats.
I will need to decide:
1. what type of boat is it?
2. How do you start/drive a boat?
3. What stuff is on a boat that I need to know about - radar, depth guage, how long the anchor rope/chain is and how to use it.
4. what the speed is i.e. if it has a top speed of twenty five knots what's that in MPH?
5. How does someone report a stolen boat?
6.Where can you hide a boat.
In the end I got the character to steal a car, I know more about cars, but the point it it's easy to do research now, when I was at uni, I did quite a lot of civil law in my first year and the lecturer would NOT allow us to use Google he insisted we went to the library and trolled through tomes and tomes of case law to research the projects he'd set us, just like he had to do when he was young.
The girl that got the best grade was held up as a paragon of virtue she had done such a brilliant job he said and he could tell that she's spent more hours in the library than probably the rest of us put together.
She told us later in the pub that she'd googled it all in three hours.
Stupid old bugger of a law lecturer was clueless - but nowadays it's so easy to research stuff online why would you bother going to the library?
Some of my recent google searches include:
How to sneak a rocket launcher out of a UK army base, How to smuggle a gun into the UK (Post it in bits and pieces from Texas in case anyone's interested), Where to stab someone so that they die instantly, how much force is needed to smash someone's skull in with an iron bar, How long it takes a body to decompose outside in February, how to deep to bury a body so that dogs can't smell it, how to make a bomb small enough to fit in a handbag.
As I'm typing I'm waiting for MI5 to knock down my door and whisk me away for questioning.!