Hi there,
There is no real easy answer here and every one has their own 'rules' so to speak. All moves one makes, should be done with the context of your own portfolio, risk tolerance, age, etc.
I'll tell you about my own approach and perhaps that can help provide some ides for yourself. First, I very much have a different approach for my 'foundational stocks' vs 'growth stocks'. Foundational stocks for my protfolio means strong companies growing the dividend. Think banks, railways, insurers, utilities and other good foundational stocks. Growth refers to those that have a higher risk profile but are poised to grow at a faster rate - think stocks like SHOP, LSPD, WELL, etc. For the most part, they don't pay a dividend.
Here is my philosophy around Foundational stocks - I don't sell. Unless there is a fundamental change to the reason why I would own the stock, I don\'t sell my foundational stocks. What about rebalancing? Well, depending on what stage you are at in your investment 'life', you can rebalance with new money. So that means new money would be put into other positions. Early in my investing life, i was heavily weighted in financials but I did not care as I had a long runway to rebalance with new money. As I get closer to retirement, I find my portfolio is quite balanced and that was achieved simply be re-directing new money into areas i needed exposure, or topping up existing positions that may have fallen in portfolio weighting.
My philosophy around growth stocks - I sell to recoup my initial capital and redeploy. Since growth stocks are higher risk, I do tend to take money off the table when I have nice profits. I have no hard and fast rule and is dependent on the company, but usually i'll look to sell half my positions once i reach triple digit gains. I might also only sell 1/3 or 1/4 depending on the stock. However, it all boils down to recouping the initial capital I put in. Then I take that capital and re-invest in another growth stock - rinse and repeat. Usually, i'll keep the remainder of the position and let it ride unless the fundamental reason to own the stock changes. Then I may chose to sell out completely. However, since I always invest with the long-term in mind, it is rare that this happens.
Now, this is my own personal approach, and others may differ. Perhaps you can gleam some ideas from this (it is a high level overview), but the important part to remember is that it has to fit within the context of your own portfolio and risk profile.
Mat