Marketing is a field requiring skill. It requires knowledge and savvy and other skills that not everyone has. That's why companies hire marketing companies --- to get the advantage of skills they don't have which will help them reach their goals. Sadly, too many companies are lured in by false expectations, though. Don't fall victim to this. Spot traits of marketing firms that should set off red flags for you.
Guaranteed Google Results
Be very careful about dealing with a company that promises you to rise to top spot on Google's (or MSN / Bing, Yahoo, or some other search engine) search engine results pages. Not only is it unrealistic to promise such a thing but there's no way to guarantee it. Even if you pay a heck of a lot of money and do achieve it, there are no guarantees you'll stay there. Further more, there are more important aspects of online marketing than just hitting top spot for a single phrase. Is it the right phrase? What will people find when they click on your link? Will your landing page REALLY entice them to buy?
Further more, what if the marketing companies' antics are considered grey hat or black hat? There are ways to get to the top of search engines fast but that aren't considered legal in the eyes of the search engines so your top spot could suddenly translate to being blacklisted altogether. A lot of time, effort, and investment could go down the drain.
Thousands of Visitors / Website Traffic
If you're promised a specific level of traffic to your website, you should ask the marketing company to be more specific. Not all traffic is equal. Watch for marketing companies making these promises because you'll want to know where that traffic will come from so you can determine how useful it will be to you. Expert marketing companies know how to get traffic that converts from a visitor to a buyer and that's the sort of traffic you want.
When you feel like you're being sales pitched, you probably are. Marketing companies should wow you with their results rather than just wowing you with their hype. Ask for proof, ask questions, and look for complete transparency so you can be certain you're dealing with a reputable company that uses ethical marketing techniques that will benefit your company rather than just benefiting the pockets of the company trying to "sell" you.