How often should I meet my direct mentor in bachelor's thesis? I am doing my bachelor's (undergraduate) thesis in a research lab. My supervisor, who is head of the lab, has assigned a junior professor and his PhD student as my direct point of contact. With both of them, I have a weekly meeting where I present the work that I have done. 

I get severe doubts while reading the literature, etc. Should I approach my PhD point of contact for this? How often should I approach the head of the lab? 

The PhD student seems willing to help. But, as a new researcher, am I supposed to ask him the conceptual doubts I am getting? The way you ask professors after a lecture? The topic of my research is completely new to me (I haven't been taught it formally before).
My undergraduate project meant I had a meeting once a week for 10 minutes... Some meetings left me with 3 weeks work... So it depends but for an undergraduate, once a week is ample. 

Some PhD students have daily conversations, others less often, but that depends on the topic, field and the people involved.