Intel is very important, as a runner and as the corp. Cards like Infiltration which allow you to peek at cards are, in my opinion, underrated. However, even if you never play with intelligence gathering cards there are plenty of free ways of gathering information to give you an edge over your opponent.
Go through your opponents Discards.
This is a great way to start to piece together the strategy of your opponent. If you are playing against a corporation, I like to sift through my opponents archives to get a sense of what traps lay ahead. If you see no traps or multiples of the same trap, you might be safe to run that iffy server. Remember, you can only have three copies of a card in your deck, so seeing three snares in their archives means you are safe from that particular card.
If you are playing against the runner, you can sift through their heap to get an idea of what options they have available to them in the future. If you count the number of event cards they have played and if it is around fifteen or so, they probably don’t have any more. Also, you can watch what cards they discard. A savvy runner will try to discard cards that don’t reveal too much to their opponent. This can be done by trashing duplicates of programs or resources that are already in play. They will try not to discard game changers or surprises that may alert the corp and thus give them intelligence to start shoring up vulnerable servers. Like escher or sneakdoor.
Another good habit is to count the influence of any off-faction cards that are being used. This can help limit the amount of surprises you can expect in an opponents deck. For example, if a NBN deck is carrying Scorched Earth, that’s four influence and any good deck will contain multiples to enhance the probability of drawing them. Therefore, that’s between 8 and 12 influence on one card! This is great information because you know the rest of the deck must be NBN cards. This helps the runner a lot. The same applies when playing against a runner. So, try to keep an informal mental tally of all the off-faction cards you have seen. Go through their trash pile frequently to help with this. Knowing what you could potentially run into, is a great advantage.
Trying to forecast what ice your opponent has protecting their servers is a powerful exercise. When you initiate this activity as the runner, you begin to think like your opponent and this is always a good thing. By thinking like your opponent you can begin to anticipate or understand their actions. The second reason, which is just as valuable, is that you begin to memorize all the ice types and their effects. Another way of doing this is to play identities that you don’t necessary like just so you can familiarize yourself with the cards and the play style.
Despite all this how do you guess what a card is when you cannot see it? There is tons of information provided by the corporation to guess what a particular piece of ice is. The easiest is by doing runs on R&D and HQ and accessing ICE in those locations. If you access a card in HQ and it is ICE and then next turn an ICE is installed, there is a high probability it is the one you accessed. Especially, if the corp hasn’t installed ICE in a couple of turns. Another way is to look at the credits/clicks available to the corp. If you are running servers through unrezzed ice, look at the corps economic situation. Could they not have enough credits to rez the ice? If this is a possibility, then that eliminates some possibilities of what it could be. Or another possibility is that the corp wants to maximize the hurt to you by rezzing it late in the runners’ turn. For example, perhaps it is a Heimdall 1.0 and you don’t have a barrier breaker but you are running it early in the turn. The corp doesn’t want to tip its hand and rez it if you are just going to click out of the damage. Another consideration is the amount of time it takes for the corp player to debate rezzing the ICE. If the game had been fast up to the point of Rezzing then it could be that the corp CAN rez it but chooses not to. The reasons for this are many but can often be reduced to a manageable few. For example, it could mean they have the credits to rez it, making the cost of the ice known, and want to protect the server but need the money for some action later and there is a level of probability that favours the corporation slightly. For example, perhaps you are running HQ with an unrezzed piece of ice and the server has 5 cards in it. If the corp hesitates and has lots of credits, this could mean that there is an agenda in there. The probability of pulling it doesn’t favour the runner but the possibility is there, hence the hesitation. If the corp couldn’t afford the ICE there would be no hesitation. Similarly, if there was no agenda, no hesitation. Intelligence.
The last reason to guess ICE is because it makes you know the cards better and this makes you a better player overall.
Overall, intelligence in any form is useful and should be maximized for your gain and minimized for your opponent whenever possible.