Most of us when preparing for a job interview tend to concetrate on the role and rarely on the employer (unless its just to get some small background). However and this is true in any industry, the employer should be equally as important.
Financial perfomance specifically cash flow. Is profitability revenue or cost driven? If its cost-driven, you are likely to suffer redundancy under the first in first out rule. 2ndly, getting spending of any type approved will be a beaurecracy nightmare. If its revenue driven, is it sustainable?
History of financial scandals: If it has been involved in scandals, this will be repeated. This is very true especially in the finance industry. UBS (the one with the largest amount of write-offs currently), has been a victim of LTCM, hedge funds and now credit crunch. Similarly Lehmans.
Does it try to get you take a paycut? They don't value you as highly as your employer. 2ndly, they don't care if you leave within 12 months for a better paid job.
What is its position in its sector i.e. is it a niche player, a big player or declining?
If you value work-life balance, try and set your interview before 8 in the morning or after 530 as that will give you a good idea.
And your prospective boss:
Does s/he understand the firm and where its going? If s/he doesn't, chances are s/he is unambitious and won't be staying long in the firm.
How long has s/he been in the company and has s/he progressed or any inkling of ambition? 5 years means s/he has experience, 10 years that s/he knows everybody and will stay there unless redundancy or retirement claim him. If he has been doing the same job for 5 years, worry. If s/he is new then you get to learn the firm together.
Does s/he ask the obvious questions i.e. about any gaps between jobs; fast-changing between firms? Job related queries?
Does s/he answer your questions properly? Remember your prospective boss is also trying to sell him/herself to you.