Well, about meditation and so on, i think a brief search in this forum, on the Net or in the library you work in should provide enough informations
and exercises to train yourself.
You may also consider the idea of practicing some Yoga, since it may give you several benefits in short time, too.
Right now i can give you only a hint. Easy to write, but probably the hardest to follow.
Trust your feelings and sensations.
I've learnt it first person. It's not easy, because when you feel a certain "something" you keep trying to rationalyze, you keep going on like
"man, it's just my impression, my mind playing tricks". And you stop trusting your feelings, or unwillingly modify the sensation you've had.
Pay attention to what you feel, accept it without trying to rationalyze. Remember it, and see what happends next. This way you'll get used to discern
between your sensations, and your mind tricks. This way you'll learn to understand your feelings, to understand what your subconscious mind is
telling you (and IF it's telling you something or not), and you'll manage to learn how to trust it.
You'll notice you're feelings are going to be more and more often right, precise, deeper, gaining many "gradiendts" you weren't able to perceive
before... well, from this point on you'll be able to proceed on your own.
I think the most important part of it all is being aware of such sensations. Personally, i begun paying attention to them since i was very young.
Can't remember the exact age, but for several years (more or less until the age of 15) i was spending my time either with my grandparents, or at home
with my parents. Very seldom i had the chance of meeting friends (just one or maybe two afternoons per week, during the weekend), so i had a lot of
time to spend with myself.
Well, i noticed that some "sensations" (i'm using brackets because they were a certain type of sensation... can't explain with words, but when you
feel it you know) often proved to be correct.
At first i didn't pay much attention to this, but through time i asked myself whether it was just a mere coincindence or not, so i decided to pay
attention to them, and slowly became more and more "attuned".
Well, i'm not going in particular details, but i can assure you that i'm happy i decided that way, because such "sensations" have helped me in
many many many occasions.
One last thing... you wrote that you felt some odd "presences"... probably you felt right. There's nothing odd or nothing bad. It's just that
"normal" people have long forgotten how to do it.