Well particularly if you're scared at the time I wouldn't try chanting or other spell work drawing on your own energy. Fear is a negative emotion and by attempting spell work fueled by such an emotion would only serve to strengthen it and actually work against you. That in itself is kind of the point of meditating prior to a spell, to calm you emotions and allow you to focus your true intent behind the spell ensuring you only use the positive emotions that you intend to.
I don't personally think you need an expert with you to meditate, I never did and it's something that comes fairly naturally. I do agree however that something may attempt to influence you whilst meditating, that's not particularly risky though. If you stop meditating part way through then big whoop, stop spiritual work and break a circle part way through then there really is a big whoop (That works much better if you can hear the intonations) as you've effectively let that spirit free and simultaneously allowed anything else to come in. Personally I feel you're more likely to need help with chanting than meditating as that's when you're actually directing your energy and the point where influence over you may make a difference.
In this case you aren't scare that why you can suppose him like that, the case he met know is different. Chanting isn't same with spell. chanting here mean you need to pray for the higher being that you believe in. or you can use word in order to calm you down, such as, may all being be happy, etc. until you can calm your self. You can try the method i suggested or you can try the method that murfle suggested. or you can try other method that feel most suitable with you
Well in what case? in meditation or when you arent meditated. Some people suggest you to asking or talk with them even when you are meditation. some suggest just ignore them because your meditation object isn't spirit ( i also suggest this). But if you aren't in meditation mode, u can ask him, where he come from, and what can you do for him. just asking
Firstly it wouldn't be clairvoyance in that case but looking into a different plane such as the spirit world, I don't know if there's a posh term for that but this is just me being pedantic anyway. How would you know that it's a different plane, I don't think that such events are all that common but I may be wrong. I think it's more likely a manifestation of something personally but only because I've encountered them more often. I don't know how you wold tell the difference between the two although one would assume that your presence in another plain wouldn't cause a particular response where as there's in ours is more likely. The obvious question though is why do you think it was a different plain/dimension and what incident(s) are you referring to?
The good news here is that I actually agree with heelingsage at last, or at least partly. If you want to know what something is the best way is probably to ask it. (bear in mind though that spirits can lie so if it sounds implausible then it most probably is)