Okay, they are two very close sounds.
If you are speaking in a normal pace and the letter is in the middle of words, then it doesn't really matter. Speaking normally, we don't give each letter it's correct pronunciation; to make speech easier and faster.
A very good example is when we use the future tense in Egyptian; we conjugate the verb in the present tense (without بـ before it) then we add either هـ or حـ . Both are correct and both can be used by the same person; it's not a matter of dialect or accent.
e.g. I will eat after an hour
انا هاكل بعد ساعة
انا حاكل بعد ساعة
But when speaking slowly, we have to pronounce each letter correctly.
The هـ is similar to the H sound in English. It is just air pushed up from your lower throat to your mouth. You can also make it by using air moving down your nose (silent) and then you add your voice from your vocal cords (pronouncing it that way will sound like humming).
The ح has no alternative. Although it shares very close features with هـ it sounds slightly different. First you cannot do it from your nose; it is always from your lower throat. To produce it, think of strangling. A light pressure that should be applied on the airway, so that the normal airflow used in the هـ letter is now strangled and has narrower pathway to go through. It is not a complete blockage of the airway, just making it tighter. Be aware of your throat, think of strangling and then try doing a هـ sound; it should come out as ح