after a few turns of play, you will have received enough cards to trade in for additional armies. the question is, do you trade them in? usually it is a good idea to trade them in later in the game, giving others a chance to trade in cards first. the time when you should trade in cards is when you are able to eliminate a foe. then you can add their cards to yours, and add to your territory. remember,  if you end up with more than 5 cards, you have to turn them in even if its your during your turn. this can be to your advantage, as it allows you to reinforce your position further as you eliminate powers from the game.

the opening in risk deals with were you place your units, and where they are concentrated. when placing units, one must consider what continent(s) they will try to attack, and how will they expand. this can be the same area, or it can be separate areas. like trying to take over Australia, but planing to expand in Europe. ideally, you will place your initial units so that you can be flexible when choosing where to expand to. one of the most important part of a war-game is to “know thine enemy”. if you understand what your enemies objective is, then you can more accurately asses where to attack. if two people are trying to attack the same continent, let them duke it out. if there is only one, then you might have a chance of getting the Continent, but it would be best to try for a different Continent, and leave enough units to delay your opponents conquest. if you confront him on the continent, you will have to use a large number of armies to defeat him.

sometimes a boarder may not be able to be defended, no mater how many units you send to it. in this situation, it is better to retreat the majority of your forces away from that boarder. i do not mean to completely abandon it, just move your forces back so that they will be able to recapture any territory lost. the most important thing is not the number of your forces, but the concentration of them. if you loose a large army on one front, then you will likely not be able to recover if you do not have another large army on that front. if you pull your army back, then you have a better chance of holding that front together. if you are making the best use of your armies, then you only have units on the font lines. so if someone breaches one of your boarders, it will cause problems.

risk is an introductory war-game. as such, it has a much more in-depth strategy than simply trying to get more units than your opponent. the first of which is: distribution. how many units do you have on each territory? the more units you have in one territory, the more effective you will be attacking from that territory. this is not because a greater size has an advantage- it is that you keep that advantage as you are advancing. if you have one eleven-unit territory attacking a five-unit territory, you might end up with 6 units in the conquered territory. however, if you had two six-unit territory attacking a 5 unit territory, and you stopped when you only had 3-units in a territory, you would have a smaller number of units in the territory after attacking. this means that your attack would stop sooner, and would also be more easily recaptured.