Well basically there a few guide lines to follow , firstly it will be hard to just determine when your plants are ready for harvest unless your experienced with the strain without either a "Portable microscope or a Magnifying glass at 30x or more" I say this because you can't see the trichomes true colour from the naked eye . This all comes down to preferences tho , if you want more of a body buzz type high your going to be looking to harvest when your trichomes are 80% milky 10% clear and 10% amber if the body buzz is what your after this is around when you wanna harvest them because even after you cut them down they continue to grow and ripen . If your going for that couch lock type stoned your going to want to wait for the trichomes to be 60% milky 35% amber and 5% clear , the more amber the trichomes are the more couch lock your high will feel . The down side is if you wait to long you will lose potency over time so its important to keep checking them almost daily . Here are some links to a portable microscope and a good magnifying glass you could use to check the trichomes you dont need these items however they will help greatly ! Portable Microscope : https://www.amazon.ca/Carson-6X-12X-Lighted-Pocket-Microscope/dp/B00LAX52IQ/ref=sr_1_4?crid=3MDR3ERTT9OKW&keywords=portable+microscope&qid=1551748335&s=electronics&sprefix=portable+microsc%2Cmi%2C171&sr=1-4
And here is the link for a good magnifying glass that will do the job as well : https://www.amazon.ca/Jiusion-Illuminated-Magnifier-Magnifying-Microscope/dp/B07KC7CVQB/ref=sr_1_22?crid=SVAPF0FPJIN9&keywords=magnifying+glass&qid=1551748406&s=electronics&sprefix=magnif%2Celectronics%2C161&sr=1-22 of course these are just examples of something that would work and to give you an idea of what you need to check the trichomes . I hope this information helps you understand when you can harvest for what your looking for in terms of high , "couch lock or body buzz" and the various tools you can use to help you check your trichomes . Over all your lined up to have a nice harvest ! -Happy Growing!