Make sure the firm you sign up with is legal, or authorised
You can do this by simply clicking the link supplied (FSA).
It will give you a register of authorised firms, a contact centre and a list of 'unauthorised' illegal companies likely to rip you off.
The FSA website: The first stop to see whether your stockbroker is totally legit
The FSA warns: " If the firm isn't authorised, you won't be able to claim a single penny from the financial services compensation scheme if the firm goes bust and you've been badly advised or the money you gave the firm is missing."
Don't worry unduly if the company you've signed up with is based in say France or Germany. Firms operating from European Economic Area (EEA) countries are also be able to do investment business lawfully in the UK.
BUT as a precaution you should use the Consumer Helpline and Firm Check Service to check the are reputable operations.
Entrusting your cash and investment to firms outside the EU is an incredibly risky business. Bear in mind the difficulty and expense of pursuing complaints - especially if the firm is unregulated.
Different countries have different laws so your rights will differ from country to country if the firm goes broke.