disabling unneeded services?

[Sivaram Neelakantan <nsivaram.net@gmail.com>]

As I had earlier posted, I have recently upgraded to Jessie.  During
bootup I see lots of stuff being started like Exim, ldap etc.  I'd
like to disable lots of these stuff if it doesn't interfere with KDE
the environment that I currently use(I used a KDE live CD install).

I have no idea what services KDE uses,what's important and what
isn't necessary.  The debian security handbook is a bit tough going
for me.

Are there any tools that guide me through disabling/enabling various
services?

And where do I start reading to make my booting faster and make my
system a wee bit more secure?

 sivaram
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