As with all forms of making coffee (and indeed as with tea bags), the strength often increases the longer you leave the bag in the boiling water. But it is still good to get a blend which adheres to your tastes.
Most bags hover around roasting levels 3 to 6. Lighter roasts are light body, have a more acidic flavour and contain more caffeine, but those at the higher end have a more bitter flavour, less like their natural taste and more from the roasting process.
Many people opt for lighter roasts in the morning and something darker for taste later on, but most manufacturers offer different blends so if you find a bag you like the sound of, opt to try a few if you are unsure.
Packets of coffee bags can come in sizes anywhere between 10 bags and 50 bags. The latter is often better for value and will suit a coffee addict or someone who will be using the bags every day, and the former someone who wants them for the occasional ease they offer (such as at work or when on a weekend break).
You can also now buy in bulk, so have around 100 bags which is great for an office.
The price of a packet of coffee bags varies wildly depending on how many bags are in the box, the brand and the roast. In general, however, you can expect to pay anywhere between 15p and £1 per bag.
The former price would be good for anyone who currently uses a filter machine or cafetiere and wants to stick to the same price bracket for the bags, and the latter is still cheaper than a takeaway coffee so either way, they are great value.