There are two main ways to make more money from your current job: do overtime and get a payrise.
Let's start with overtime first. In these days of recession, it might seem difficult to get overtime authorised, especially if you work in an industry with too much production, such as car manufacturing, which is looking to cut back on the hours people work. However, if you work in customer services there might be scope for extra hours, especially if your company has laid off some staff. What usually happens in these circumstances is that the number of customers wanting their problems sorted out will remain the same, and to get the work done by a smaller staff, management has to authorise overtime.
Getting a payrise in a recession is a lot more difficult. Indeed companies will be looking to freeze salaries, citing the downturn as an excuse, and hoping that there is sufficent fear amongst their staff to accept the freeze. The key to getting a payrise in these circumstances is to make yourself indispensible.
First ask yourself if your job is essential to the functioning of the company. If you work in a sales role, or customer-facing role, chances are it is. Ditto for the IT people in software companies, and engineers in hardware companies like Sony or BMW. But if you work in the PR deparment, or look after in-house travel for the executives, or are in personnel, you can be cut from the workforce without the customer noticing a thing, and in these roles you'll be lucky to hang on with the same pay, let alone get a payrise. If you feel your job is inessential, the first thing you need to do is to try to get a transfer within the company to a role that is more relevant to the company's survival and future.
Whether you are a key worker or not, everyone should make sure they become indispensible in their job. Become a database of knowledge about everything to do with your company and job. I used to keep a file in my desk, where I noted any new information I learnt about the company's products, solutions to problems I had encountered, quirks about the legacy computer systems, anything that I thought might be useful to note down in case it came up again - and these things always come up again and again. I soon became the go-to person for all and sundry, with even senior managers coming up to say, "You've been here a while, can you tell me about xyz". When companies get rid of staff or have a high staff turnover, institutional memory is lost, but the old legacy systems still need people to maintain them.