Borussia Dortmund phenom Erling Braud Haaland has told potential suitors what they must do to secure his signature.Manchester United and Real Madrid are both interested in signing the 19-year-old striker.Speaking to Eurosport, the Norwegian said: "You've got to time how good you are, how good the club is, the people there, how they take care of you, how they help you evolve."There are a lot of factors and I remember when we discussed Salzburg and different clubs we figured out very early that Salzburg was the best option."And I've always thought 'I can't overrate myself'. That has always been important to me, saying, 'yes, I'm good, but there's a lot of good players out there', so that has always been very important to me, to not think I'm better than I actually am."He added: "I'm feeling very well, and yes, it's been like a dream, but there have also been matches in the past that haven't been that good, so it hasn't been perfect."But I've had some very good years. Today I'm very happy, and I still have very good people around me, if not better, so I'd say this is just the beginning and there is much more to come."