As soon as Guild Wars 2 will be released, what content of my Guild Wars 1 account can I transfer over to Guild Wars 2?
Actual characters cannot be transferred to GW2, though you will be able to reserve character names. If you purchase Guild Wars: Eye of the North, you will have access to the Hall of Monuments. The HoM is a way to track various achievements from GW1, such as miniatures collected, prestige armor/weapons acquired, titles and accomplishments you've achieved, etc. ArenaNet has confirmed that your character in GW2 will benefit from any accomplishments you have logged with the Hall of Monument by linking your two accounts. The bonuses you can acquire are account-based, not character-based, so if GW1 character A got the Tyrian Explorer title and GW1 character B got the Canthan Explorer title, you will still get the benefit from both characters' accomplishments in GW2 as long as you've logged those accomplishments in the HoM. Happy achievement hunting! :)
Additionally, there is now a website where you can fill in your character's name and your GW2 rewards will be calculated based on what is currently in the Hall of Monuments. Calculations are based on account, so even if you fill in a certain character's name, the rewards you are receiving are based on your account as a whole. You will be able to continue adding to the HoM after GW2 releases.