As a beginner, how do I decide what percentage of my portfolio should be in bonds?

Start with your time horizon and your stomach, not a formula. The classic 'age in bonds' rule (a 40-year-old holds 40% bonds) is now widely seen as too conservative given longer lifespans; many advisors suggest something closer to 'age minus 20' or letting a target-date fund decide for you.

Money you won't touch for 15-plus years can be mostly or entirely in stocks. Money you'll need in 3-10 years wants a meaningful bond cushion. The honest test is behavioral: if a 40% stock drop would make you sell, you hold too little in bonds. It is better to own a more conservative mix you can stick with than an aggressive one you'll abandon in a panic. The Investor Profile assessment at wealthserene.com/assessments/investor-profile can suggest a starting allocation based on your goals and risk comfort.