One of the most simplest errors I use to make when preparing herbal tea is not using enough tea or allowing it to steep it long enough. I've learned a few tricks over the years when preparing herbal tea to get the most out of it.
If you are using bags, I recommend 4 to 6 bags per quart jar or 1/2-1oz of loose herbs (roughly one handful). Steep up to 20 minutes to make tea, 4 hours to make a medicinal infusion (especially if you nursing & want to increase supply); if the herb has a lot of roots/bark (dense herb) steep overnight room temp for 6-8hrs to make a decoction.
One easy way I add this to my routine is right before I go to bed, I put my herbs in my jar with raw honey or coconut sugar. Pour in my hot water and let it sit room temperature overnight. If the herbs you are using are mucilaginous herbs like marshmallow root, mullein and slippery elm use tepid water instead of hot; infusing mucilaginous herbs can make it really "slimy" and it may not be palatable. In the morning I strain the tea and add ice. I find it much easier to drink my herbal infusions when iced, some actually taste a lot better too!
I find it easiest to use a french press when making herbal infusions with loose tea. I keep three sizes on hand for all my needs; 3 cup, 8 cup and 12 cup. You can use a french press for more than coffee - who knew?
I think you will find this video helpful on how to prepare tea with loose herbs in various ways.
If you are expecting or know someone who is, please check out this post Five Herbs for Pregnancy