Create 10 practical strategies that self-employed individuals can use to legally and effectively optimize their tax burden in order to increase financial flexibility and efficiently prepare their tax returns.

Context: [tax optimization, self-employed, tax burden, business expenses, tax benefits, tax return, allowances, investments, income surplus calculation, financial planning]

Goal: [reducing tax burden through targeted measures, utilizing tax planning opportunities, practical tips for bookkeeping and tax returns]

For each strategy explain:
1) a concrete approach or measure for tax optimization (e.g. deduction of business expenses, use of allowances, investment deduction)
2) advice on practical implementation in the daily life of self-employed individuals
3) tips for avoiding common mistakes and complying with tax regulations

The strategies should:
- be easy to understand and directly applicable
- be specifically tailored to the needs of the self-employed
- be useful for both beginners and experienced entrepreneurs
- contribute to the sustainable improvement of the financial situation