The water is very important to the resulting beer. After all, beer is mostly water. If your tap water tastes good at room temperature, it should make good beer. It will just need to be boiled for a few minutes to remove the chlorine and kill any bacteria. If the water has a metallic taste, boil and let it cool before using to let the excess minerals settle out, and pour it off to another vessel. Do not use water from a salt based water softener. A good bet for your first batch of beer is the bottled water sold in most supermarkets as Drinking Water. Use the 2.5 gallon containers. Use one container for boiling the extract and set the other aside for addition to the fermenter later.
This is another involved subject. There are many varieties of Hops, but they are divided into two main categories: Bittering and Aroma. Bittering Hops are high in Alpha Acids (the main bittering agent), typically around 10 percent. Aroma Hops are lower, around 5 percent. Several Hop varieties are in between and are used for both purposes. Bittering Hops are added at the start of the boil and usually boiled for an hour. Aroma Hops are added towards the end of the boil and are typically boiled for 15 minutes or less (Finishing). Hops can also be added to the fermenter for increased hop aroma in the final beer, called Dry Hopping, but this is best done during Secondary Fermentation. A mesh bag, called a Hop Bag, may be used to help retain the hops and make removal of the Hops easier prior to fermentation. Straining or removal of the Hops before fermentation is largely a matter of personal preference.
Published beer recipes often include a Hops schedule, with amounts and boil times specified. Other recipes specify the Hops in terms of AAUs and IBUs. AAUs are a convenient unit for specifying Hops when discussing Hop additions because it allows for variation in the Alpha Acid percentages between Hop varieties. For example, if 7 AAUs are recommended for the Boil (60 minutes) and 4 AAUs for Finishing (15 minutes). This is assuming the use of Unhopped malt extract; if using Hopped, then only add the 4 AAUs for finishing. These amounts correspond to 22 IBUs for the boil, and 1.25 IBU for the finish. IBUs allow for variation in brewing practices between brewers, yet provide for nearly identical final Hop bitterness levels in the beer.