Resources win lanes. The temptation to build items that will last forever is strong, but if you're on a hero like Lich, CM, or other lane bullies (aka spell spammers), take full advantage of your kit and buy out the mangoes and clarities. Keep mana and HP on yourself and your core and watch how easy your lane gets. (Be courteous of heroes like SF in your games, who also depend on spell spam in lanes.)
Wards save lives. Around 5m I'll normally place an obs not ON the gate, but in a spot that dodges gate sentries and shows the lotus pool and incoming traffic from the gate. I also like wards down the lane, though not in a spot that will be obvious. Another good defensive ward will show incoming TPs from enemy t1. If heroes like NP or SB are in the game, you may want to ward a bit earlier. Ward according to where you think the gank will come from based on who the enemy heroes are - especially if you plan to rotate or leave lane. P1 is safest with 2 obs at least.
Rotations are amazing if you can pull them off. As p5 it's hard to get away at 6, 8, or 10 for the mid rune, but it's something to consider if your mid or the enemy mid cares about runes. For example if the mid heroes are things like puck, the spirits, qop etc, a rotation to secure the rune and deny the enemy can ensure your mid wins the lane. Two rotations and it's pretty much over for enemy mid. Definitely worth doing if you're with a p1 that can be left alone for a moment / can pull a stacked small camp for themselves.
Lotus isn't worth your life, but wisdom is. If enemy offlane is weak or absent, get p1 to come with you to secure enemy wisdom. If they start TPing in, just get back. Another play my stack likes is for our mid (if possible) to TP to enemy wisdom and fight for it. Since this play is unexpected - and especially if we've won sidelane/mid - we can secure both wisdom runes and some kills for our mid by doing this. It's not always possible, but it is very worth it if you can manage.
If your p1 is forced out of the lane (enemy Timber hits 6, it's undying + anything, etc) and has to jungle, don't panic. Many p1's can afford to do this. My typical response if my lane is too weak to live and there's no way for other lanes to support us is to go torment the enemy cores. Typically I'll rotate to play with p3 and 4, thus forcing rotations from enemy supps/mid and giving my p1 some breathing room (we call this plan B; it's not ideal, but if you need to use this option, it's good to know about it.) Anything is better than continually dying in a lane, so if you absolutely can't manage it, give it up and tip the balance elsewhere.
Even if my p1 is safe in lane, I try to rotate out as soon as possible and pressure enemy p1. It's a bad gamestate for you if the enemy supps are reinforcing p3 against your p1 and p5, so you want to make sure the opposite happens. You do NOT want people in your safelane anywhere near your p1, so make sure enemy attention is on their own p1 and their rotations are defensive (to try to stop you/kill you). Try not to feed while doing this; it's mainly a 'kick the hornets' nest' type of play. Any kills you get in the process are the cherry on top.
No-no zones for wards exist all over the map. Direct forest entrances/river ramps/pillars are a no-no for me unless my team plans to push/play around it and defend it. Otherwise, it's just free money for enemy supps. Try and find cliff "lips" and ledges that seem out of the way - often these dodge enemy sentries and, though they're a little bit tricky to click on, you'll get valuable information from them.
Speaking of information, don't give the enemy any information that you don't absolutely have to (or if it doesn't matter). For example, don't show up to a gank or a bait and announce your presence with a VS W or a powershot. This gives the game away. Instead, be stealthy; don't show them your rotations or TPs, don't show them you going in or out of their jungle (because a good enemy supp will assume you warded), and generally keep a TP on you so you can quickly reinforce your team. The less the enemy knows, the better your chances of winning. (Conversely, giving the enemy disinformation is a next-level tactic. Showing one or two heroes on a wave while you're doing a smoke gank gives the enemy false confidence, whereas if all heroes are missing or if only a tank is showing with nobody else showing, a gank/bait is too obvious).
Use smokes wisely, not just at any ole time. Play around timings, first your team's (e.g. if LC is close to blink let her finish it) and enemy's (e.g. if chrono/ravage/GS is down, run at them). Smokes are extremely useful with deep wards of your own, as you can get valuable info on the location of farming cores, as well as being useful for walking through enemy wards you know are there (since the presence of their obs will give your enemy the confidence to keep farming, since people typically don't expect a smoke unless ALL heroes are miss).
Your job is, essentially, being in the right place at the right time. To do that, you must anticipate what the enemy wants to do. To do that, you click on enemies throughout the game to see what cards they're holding. All the information is right there if you just take a moment to look. Check enemy supps for wards, smokes, glimmers, dust, gems, etc. Check all enemy heroes for "go" items like blink, which indicate that a blink reveal gank is probably coming. Check cores throughout the game for big power spikes like BKB, satanic, etc. If you stay on top of the information in the game, you can control the game. That's basically how I see my job as p5.
Hope that helped, there's more but I like the number 10. Gl
