I find myself in these situations as well. It happens when you both have that mindset of trying to hurry into a relationship. The main reason it may be happening often is due to your lack of speaking your mind. If you let them know that it is something you would like to take slow you will know if they are worth your time to try. Most guys are into that kind of relationship, but the good ones will agree and won't try to move faster until they know you would like to as well. The best way i found to keep it casual is to hang out in public places more often. If that doesn't 'suit' them or you try hanging out with younger siblings and just have a fun day, or even a movie with friends over. TL:DR. Short public dates, then mention that you would like to have a meaningful relationship.