Holy cow, I wrote a book!
Random number generation is hard.
That's why you should leave it to the experts.
But even if you choose a good random number generator,
you still have to seed it properly.
The best random number generator in the world isn't
very useful if people can guess the seed.
seeding the random number generator with the current time
is not very secure;
it's not hard to guess the current time!
So it's important to throw something unguessable into the seed.
As the above paper notes, just the time and process id are not good
So what should you do? Don't ask me; I'm not a cryptography expert.
Here are some suggestions from other people.
Maybe some of them are good, maybe not.