OK TS , I will tell you all I have done...

Number 5 - her things accidentally end up with me (risky to pull off .. but we all need excitement if our life right  
Number 4 - I keep talking about the future and then stealthily bring her in that image.. 
Number 3 - Check her out with her being aware   
Number 4 - Mention her name in a circle of her friends more than two times
Number 1 - When I see her I give her a longing look in her eyes.. 

Now if you want to know the effectiveness of it , that is a whole another story bro !!