WATCH_DOGS

The 60 seconds for Intrusion are vital.

This is arguably the most important step of a successful hack. Use every bit of that time to not only distance yourself from the player (watch for the red zone as you can only go so far from the player and still begin the intrusion) but find a good hiding spot. Here's some major points to having successful hacks:

Stay away from high-end vehicles.

This is one of the biggest dead giveaways to being spotted, while high-end vehicles are relatively common especially in certain areas of the map, some areas they are very rare and will be a huge red flag to the opposing player. Stick to common vehicles, trucks, SUVs and city vehicles help out more as they are more difficult to directly see into and can hide much easier than a hatchback or sedan.

Distract, distract, distract.

Traffic lights can be a huge help to causing major distraction to both the player and the environment. When there's a multiple car pileup in the middle of the street, people will be scattering all over as well as many more cars being in the area to hide in / around. Other distractions such as blockers, pipes and explosions can work, but more often than not the player will realize you are within a close range of the incident rather than be affected by it.

Don't panic, but be cautious.

There's been multiple times where the player has been within a matter of feet from me while hiding behind an object and by tweaking my position slightly or simply holding my ground, they were none the wiser. If you seriously think you're in a good spot, don't blow it by panicking just because he is close to you. Unless you time a getaway perfectly that they cannot see it, more than likely you'll be spotted. These are the absolute best times to cause a distraction as they will turn their complete attention away from their current area.

Blackouts are awesome.

I highly recommend unlocking this ability and having it ready for any invasion. Causing a blackout, especially at night is arguably the best distraction you can create; people panic, all lights go out, there's multiple car accidents, and the player's Profiler needs an even closer proximity to ID players.

The environment can work for you just as much as against you.

Certain areas of the map are much better for invasion than others. The suburbs offer many backyards and building rooftops, parking garages are excellent to shift levels quickly, train stops also offer high, mobile vantage points. However, the open areas outside of the main city are not so great, vehicles are usually the only and best hiding areas and will get you spotted relatively easy, same goes for certain areas of the main city that are mostly skyscrapers as you have no areas to dart around other than the occasional bus stop, magazine stand or car. This ties into the final tip:

Sometimes you get put in bad scenarios that heavily work against you.

Since you can be put in any part of the game during basically any part of player action, occasionally you're in a shit situation with little option. I've been put in a super car on the highway with the player already 3-400m away, on the docks while the player is in a boat in the middle of the water, or on a two lane road in the hills where there were so few cars that the player knew who I was instantly. In these situations, just try to do your best but don't expect anything spectacular; anyone who has played Dark Souls definitely knows what a ganker is and this is basically the equivalent of the game ganking you.

The other guide here is great, but i wanted to share my strategy:
Find an "normal looking" car, drive as slow as the NPC's ( when the player can see you ), drive up close.. hack.. drive as far away as you can.. initiate, and park nicely on the side of the street.. Only ONE of 11 people i hacked found me.

Try and find a large vehicle like a pickup truck or a delivery truck and crouch behind it. Always position yourself out of the other players sights by moving around the vehicle. Being in a crowded area helps but you should be able to successfully hack another player even in an open area with this strategy.

I posted the same solution on TA for x360 & Xone. Posting the same here.
Easy way to fool other players is to hack them and initiate the download then go to the edge of the circle and look for a parked car(there will be one always else take a car and park). From the edge of the circle you will have to worry about just one side from where the player will come looking for you. just take cover behind the corner of the car and have a watch on the player. If he nears you, just press X and switch corners and move in circles around the car evading the player easily. Even if the scan circle reduces, player will have no idea you are taking cover and switching sides behind car.