Not to fear. There are plenty of ways for you to figure out an appropriate number. You need to be prepared for the question at all stages of your discussions with the potential employer. You could be asked for your salary expectation at any point in the process, even in a preliminary phone interview.
How to arrive at that magic number? It is time to do some research. First, are you looking at an in house position, a law firm position, a government or non-profit position? What is the size of the entity (law firm, company)? What part of the country are you looking in? What is the industry sector (Insurance, IP, Corporate, etc.)? All of these variables will help you arrive at a number.
Typically, in-house positions, government and non-profit sector attorney positions pay less than large and mid-sized law firms. Federal government salaries are often determined on a pay grade basis, and are publicly available. State and local government salaries are also often publicly available, although they can be harder to find. In-house positions for larger corporations tend to pay less than large firms, and more than government positions. For smaller companies, in-house salaries are all over the map.
Large, full service law firm salaries in larger cities tend to start in the $130k-160 range for associates. Salaries for these large firms may be less in smaller cities, because the cost of living is proportionately lower. Sometimes, law firms, even national law firms, that specialize in certain areas of law can pay below market. For example, boutique firms specializing in insurance defense, toxic tort, personal injury, family law, and labor and employment law sometimes pay less than the salaries referenced above. IP salaries tend to be a bit higher than average associate salaries.
Small law firms and small company salaries vary widely. A start-up corporation, even in a large city, may pay as little as $40k while it is getting ramped up. Likewise, I have seen small law firms paying as little as $35k to start. Plaintiff-side firms sometimes pay little in the way of salary, but allow opportunities for associates to cultivate their own clients, and get a cut of what business they bring in.
In addition to talking to attorneys in the market sectors/cities/entity types you are targeting, you should do all the online research you possibly can. Here are some helpful sites, but keep in mind that the information may be outdated or even wrong. Still, if you read enough of them, you can get an idea of an appropriate starting point for your salary negotiations.
Your law school may also collect salary data from its alums, so call your school’s career services office and ask what salary information they have on file.
Still feel like a deer facing oncoming traffic? Think about giving a salary range. Whatever number you arrive at that would be comfortable for you, go a little below that and a lot above. For example, if you would be happy with a salary of $70k, give a range of $65-85k. The employer will probably not come in at your very bottom number, and may come in somewhere in the middle of the range, so your offer may be higher than what you would be happy with.