As for bubbles, it’s probably difficult to know all the ones which exist and when they’ll pop. There’s been a real estate bubble in China for the last couple years (google ghost cities china), but who knows when/if it will pop & what it’ll impact. (The government’s been enacting policies trying to deflate it.) So the next best thing is to just be prepared with exit strategies (Selling, not Holding) if your portfolio performance is being threatened.
The 10% correction you’re waiting for may not come for awhile, and it also may have already occurred - Feb to Mar, the Dow dropped nearly 800 points, see the 6mo, 1yr charts. We might be due for a small pullback after the last 2 weeks of strong gains, but all other things being equal, unlikely a major correction. In any case, I don’t usually try to predict what’s going to happen too far out ahead – I only try to interpret what’s happening now. Only rarely do I make higher certainty predictions (Jan, when corporate earnings were very good, Oct before the Nov elections, 09 April when the Dow rebounded strongly from 6500-8000 and a W recession was less likely).
Knowing when to enter or exit a market or stock depends on Knowledge, and imo the only way to get that is to follow the market or a sector every day. You mentioned YGE, a Chinese Solar. In Jan I went big into that sector (40%, with TSL, JKS, SOL, JASO, LDK, & SOLR), because during pre-earnings season, LDK pre-announced record earnings, and the whole sector shot up that day. I did research, and found that most companies were doing well, but undervalued compared to American counterparts with 2-4x the p/e. After the sell-off in late February (I held too long, and eventually sold all for only a small gain), I went back in soon after the Japan nuclear incident and the selling reversed. Then Germany (largest market for solar) & Merkel reversed its nuclear policy, and last weekend the Green Party scored a state victory against the incumbent party, the first in 60 years. My point is, Knowledge reduces Ignorance, and thus reduces Fear.
If you’re still uncertain about entry points (whether the market or a sector-stock), you can always scale in gradually. No need to go in all at once & lock yourself in with all your available capital. Eg, if you’re thinking of RSH, you can buy 100-200 shares now, and the rest later (or not). You can do the same on your exit, taking some profits off the table after a sizeable rise. As the Wall Street goes, “Buy (and Sell) to your sleeping point.”
Varying levels of certainty call for varying levels of cash positions. Right now, I’m 20% cash, which is what I’d consider slightly above my normal 10-15%; I’m usually never “All In”. As of now, I’m currently Holding all my positions, but I’m always ready to pull some sell triggers to protect a certain % of my current YTD gains or if my sectors-stocks show signs of weakening.