Learning a language is a big undertaking. If you don't already have a language that you want to learn, it's worth putting some thought into choosing one that will best suit your needs.
Knowing a foreign language can be useful in a lot of situations, so the first thing you should ask yourself is what situations are you preparing for? If you're looking to move up in your company and the firm does a lot of business in Germany, it makes sense to learn German fast, because that's a language you will use in the future. Alternately If you have no reason to do so, then why learn french? If you don't have a reason to learn a language, then you won't have the persistance you need to practice and build up your abilities.
In many situations, though, there are a lot of languages that could fit your needs and help you out. For example, if you want to be in international business should you learn Mandarin or Hindi? Or perhaps an African Language, or Spanish or French....or any language ever. In these situations it's easy to stress yourself out, because there are so many options. At this point it's good to remember a few things:
1) This is just learning a skill that will help you out. It's not like your making this part of your identity or anything. It's like learning how to drive or learning algebra.
2) There's really no penalty to choosing the "wrong" language. Any language you choose to learn will be useful in some circumstances and not all that useful in other situations. The best you can do is make a guess at which language will win out. Even if you have to learn still another language in the future, having already learned a language will make learning a third language easier, since you will already be familiar with the learning process.
A good way to narrow down languages is to look at statistics. This can ground you because they are hard numbers, as opposed to vague, complicated potential future plans. Some relevant statistics about languages are : how many native speakers are there? How many total speakers are there. Is there a widespread diaspora of speakers? Economically and culturally, how important are the countries where the language is spoken? Are these countries up-and-coming?
Other things to consider are the ease of learning the language and the the number of resources available. If you are torn between learning Spanish and learning Arabic, for example, it would make sense to learn Spanish. Spanish is easier to learn for English speakers: it uses the same alphabet that English uses and has a relatively simple grammar. Arabic has neither of these. There are also more resources for learning Spanish and a greater availability of source material and native speakers in most areas of the US.
It might be appealing to go for the harder of the two, but it's already going to be a challenge to learn your first foreign language. It's a good idea to deal with these challenges before adding on the additional difficulties that come with a language that is harder to learn.