It depends, of course, on why you want to learn a language, the degree of proficiency required and how quickly you need to acquire a capability.
Some students may require only basic "survival" standard - how to book a table or room, call a taxi, ask for and understand directions. Others may only need to be able to read or listen to the language.
Others again may need to raise their existing knowledge, supplement it with technical vocabulary or simply maintain it, while some may need intensive training prior to transfer abroad, or for a specific project.
Lessons may be conducted in small groups, pairs or one to one, depending on how intensive the course needs to be, the time available and budget, and will normally be supplemented by homework.
Bear in mind, however, educationists say that once past the age of 30, few people are able to achieve complete fluency unless they are immersed in the new language.
Some companies provide intrensive language learning. At Dresdner Kleinwort Benson 90% of tuition is on an individual basis.
Says DrKB's head of training Amanda Whiteford: "One-to-one is more intensive and produces quicker results."
Grahame Cook, head of equity capital markets at WestLB Panmure, who has been learning German for a year in his lunch breaks on his weekly visits to Düsseldorf, agrees: "It has got to be pretty intensive because of the opportunity cost - the time you're investing."
The consensus is that a native speaker makes the best tutor, not just because of their grasp of the language, particularly colloquialisms, but because of their insight into body language and customs.
But learning a language as an adult is hard work. If you're not resolved to stick it out, you'll "fade" quickly.
Linguarama's Virginia Withers says the four elements that affect progress are motivation, ability, homework and exposure. Weakness in or consistent neglect of any one of these may lead the student to lose interest and drop out.
WestLB Panmure's Cook believes motivation is key: "People in investment banking are goal-oriented. If you set yourself a goal, you do it," he says.
Withers says time is the biggest impediment. "Students need to devote time to language study if they are to move forwards. People often start off with a very high level of enthusiasm, but there will always be plateaux, periods of consolidation when it's less exciting and motivation falters."
Tuition may be for anything from one-and-a half to six or more hours a week, depending on the individual case and, of course, an intensive course may be full time.
However, Linguarama heavily discourages lessons of one-and-a-half hour's duration. Says Withers: "Short lessons are unsatisfactory for both trainee and trainer. We find that a lesson of three hours is more productive."
If you're already holding down a demanding job, which may itself be new to you, fitting in the hours required each week, over an extended period, will not be easy.
Cook remains upbeat. "You can achieve reasonable results from being semi-fluent, if you put your mind to it, in 18-24 months," he says.
The "ideal" time to learn is a time that least intrudes on the business, which effectively means either before or after work or at lunchtime - but tutors often offer flexibility to fit in with the student's availability.
Yet, even that may not help: as one banker who took twice weekly lessons in Japanese for six months in Tokyo admits: "When you've got a massive day job, 8pm is not a good time to study any language, let alone a complex one like Japanese."
Cook of WestLB Panmure admits that discipline is required to keep up the German lessons in the face of work pressures.
"It is all too easy to find a reason to cancel. If you don't keep up the lessons regularly, you cannot expect to make progress," he says.
Cook uses his German regularly and supports his study by daily reading of Handelsblatt, a strategy that Withers considers vital. "Unless you're using the language, you can't maintain it," she says.
Perhaps predictably, the dropout rate is high, particularly among students learning in groups for whom the language is not absolutely necessary to the job. One language school estimated that only 20-30% of such students keep up their lessons.
Dresdner Kleinwort Benson's Whiteford says: "People who find it a problem usually drop out very quickly. Those that pursue it are very dedicated."
Meanwhile, another banking group has announced that, while it still supports language learning, it will claw back its subsidy if a student attends less than 80% of lessons.
The suggestion has apparently resulted in a "noticeable improvement in attendance".