https://www.bing.com/images/search?view=detailV2&ccid=ew...Map from IGN to help you nail down the locations of these items. Most are fairly straight forward in their approach, use the tools given as you progress and back track through the game areas. Quick color quide for opening areas:
Green- Grenades
Purple - Foam
Red- Missiles
Blue- Hyper Speed (these can be tricky, but there is always a way)
Yellow - Regular Gun fire
The map will guide you to the correct spot. Once you get there as said earlier, most are straight forward. Once you are in the correct area if you have difficulty finding it, remember there is more to the screen than you can see sometimes. Some areas have open tops, some have water that you can use to swim under walls, etc. Happy Gaming :)