In USA, e.g. EB1 application, a good lawyer with good letter writing skills can be the difference in getting a green card and not. In places like Canada, Aus, NZ, which have points-based immigration, no agent can magically increase your points (e.g. CRS score). The best they can do is figure some (hopefully legal) workarounds to increase your chances of getting ITA; I can’t think of any at the moment, other than getting a PNP or getting a job.
The best option is to know the process yourself so you’ll know if it’s even feasible before you pay money to the agent. Remember that before you submit your final documents you don’t really have to pay anything to CIC, you just need to spend money for getting the documents, ielts, medical exam etc. While submitting the documents you pay around CAD $1000. So you’re already paying close to CAD $2000 for the application itself, unless that’s covered in your agent’s fees. Ask then about it.
CIC will refund your fees if your application is refused under certain cases (http://www.cic.gc.ca/english/helpcentre/answer.asp?qnum=612&top=4), they won’t if they start processing application and it gets rejected. So, check if your agent guarantees money-back if your application doesn’t get processed; that’ll tell you immediately if the agent intends to pocket your refund or not.
Another important thing to remember is that Canada has a strict policy against misrepresentation (5 year ban for all visas) if caught. If the agent is not trustworthy and does some “jugaad” which turns out to be misrepresentation, then you’re screwed!
Canada immigration process is very transparent and I would suggest you read all the options on the CIC website, including EE, PNP etc. It’s best to educate yourself and it might help you separate genuine immigration lawyers from fradulent “agents”. Also, if he’s not going to do anything and just going to send everything to the lawyer in Canada, you can do this yourself without paying an agent and directly contacting with the lawyer.