Your total homework grade has the same weight as an hour exam; your final exam will have the weight of two hour exams. Your lowest hour exam grade (or your homework grade if it is lowest) may be replaced by your grade on the final exam if this helps you. Your course grade will be the sum of your hour exam grades and your homework grade (the lowest of these four grades being replaced by the final exam grade if this helps) plus twice the final exam grade, divided by six.
Each homework assignment will be marked in the following way: you get 30% for handing it in, then you get a percentage of the remaining 70% determined by your performance on the assignment. I (or a grader) will mark 3-5 randomly selected problems from each assignment; you can always request that I look at your solutions to other problems. Your homework grade will not be scaled or adjusted in any other way. It is seldom the case that a student's lowest grade is his homework grade, if they do their homework regularly.
Don't assume that these are the only times when you can get help! I am generally in my office the entire working day (I take either the 4:40 or the 5:10 bus home) and I am never offended by a student asking me for help if I am in the office (though I may help only briefly if I am very busy).