Not usually, no. Depends on how suggestible you are (e.g. easily led or hypnotise-able), how credible and persuasive the 'practitioner' is, and the situation you want to change the outcome of (i.e. whether it's even possible in the first place, no giant obstacles, for example).
It works on the principle of Mind Over Matter and self-fulfilling prophesy via positive visualisation (the type top athletes are coached in). If you wholly, heart and mind, believe that a love spell just can't fail, it can affect you by giving you an increased air of confidence and relaxed-ness (both of which are alluring and intriguing) and better focus.
Here: "A self-fulfilling prophecy is when a person unknowingly causes a prediction to come true, due to the simple fact that he or she expects it to come true. In other words, an expectation about a subject, such as a person or event, can affect our behaviour towards that subject, which causes the expectation to be realized. In one study regarding self-fulfilling prophecies, psychologists led some male college students to believe that a female student was attracted to them and others to believe that she was not attracted to them. The social psychologists later observed interactions between the men and the female in question. The woman was much more likely to act as if she was attracted to the first set of men. Why? Because the men who thought she was attracted to them acted in a way that seemed to lead her to actually be attracted to them."
Unfortunately, now that I've explained the science behind it and thereby removed the element of blind faith, any "spell" probably WON'T work. There again, saying that, the fact you were sceptical/science-minded enough to even ASK whether and how it works goes a long way to demonstrating how it probably wouldn't have worked on you, personally, anyway.
How much is this (I assume?) person saying they charge - as a one-off total, note - and what legal purchasing protection do you have? You have to be careful, there are a lot of con artists out there.
If you REALLY want some love interest to reciprocate your feelings (assuming he's single and available and with nothing actually standing in his way) then the best way is the oldie: have a mutual friend (one whose judgement he trusts more than not but whose loyalty lies more with you) do you the favour of deliberately mentioning in his ear (in an "ooh-ooh!" way) that s/he *suspects* you might have *started* to have feelings for him *that bit* greater than platonic friendship, what does he think, has he noticed anything?
That should get him looking.
'Suspects', because then that creates Intrigue (men love it). 'Started' and 'bit' and 'not quite sure' because then that represents a viable Challenge (ditto), a way for him to win something over due (cough!) mainly to his own 'cleverness and prowess' ("Hah, she was only slightly interested in me, and even then, wasn't sure, but once *I'd* worked my manly magic on her she was smitten!"
. But obviously that mightn't work if he finds you the complete opposite to his cup of tea or has already strong feelings for someone else. Again, depends upon how manipulable HE is, normally.
Alternatively, there's the '3 second look': Look at him side-long (e.g. with him to your right). If/when he notices and looks back, wait half a beat with eyes locked and then turn your head rapidly down and to the left (as if shy/embarrassed). Immediately count in your head at normal talking pace, 'One elephant, two elephant, three elephant', then, still keeping your head slightly down (think Princess Diana), take another, what looks like, sneaky peek (before repeating the shy looking away). If at this point you've caught him still looking or taking glances at you, it's working... in which case, do it a second time. It's a kind of eyeball strip-tease. Your behaviour there suggests this: I want to but I shouldn't/daren't, eek! Again - a conquerable challenge.
However, fear can be infectious. So the thing to do once your eyes catch that second or third time (no more than 3, btw) is to crumple into a grin, perhaps preceded by making a bit of a silly face (to break the ice and signal that you're approachable/don't bite), like playfully slightly sticking your tongue out before smiling/giggling warmly.
The overall affect should be, 'Can't take locking eyes [too powerful], but can't stop looking, regardless'.
None of the above guarantees any potentially resultant date or relationship will work out, though. It's just the 'carrot'. And the trouble with carrots is, they can attract asses as well as stallions, when what you want is the latter. So, assuming you've asked this question because you fancy some guy who 'doesn't know you exist' - wouldn't you rather he actually fancied you back naturally to begin with and made the first move (as well as from a place of absolute free will)? I mean, how would you ever be able to trust his feelings were 100% genuine and therefore liable to last and be acted from?
The 3-second-look manoeuvre is the least manipulable and more healthily productive of the lot, IMO, because, really, it relies more on harnessing what might already be there (whether he'd been aware of it previously or not), rather than creating it almost wholly artificially.
10p, please. (Paypal or debit card?) (joke)